style: no longer use backquotes

* README, REFERENCES, TODO, configure.ac, data/README, data/bison.m4,
* data/c++.m4, data/c.m4, data/java.m4, data/lalr1.cc,
* data/lalr1.java, data/yacc.c, doc/local.mk, etc/bench.pl.in,
* src/conflicts.c, src/files.c, src/getargs.c, src/gram.h, src/lalr.c,
* src/location.c, src/location.h, src/muscle-tab.c, src/muscle-tab.h,
* src/output.c, src/parse-gram.c, src/parse-gram.y, src/print-xml.c,
* src/print.c, src/reader.c, src/reduce.c, src/scan-skel.l,
* src/symtab.h, src/system.h, src/tables.c:
Use single quotes, as currently recommended by the GNU Coding Standards.

data/README

@@ -27,7 +27,7 @@ Currently, the supported skeletons are:
 These skeletons are the only ones supported by the Bison team.
 Because the interface between skeletons and the bison program is not
 finished, *we are not bound to it*.  In particular, Bison is not
-mature enough for us to consider that ``foreign skeletons'' are
+mature enough for us to consider that "foreign skeletons" are
 supported.
 
 * m4sugar

data/bison.m4

@@ -313,7 +313,7 @@ m4_define([b4_define_flag_if],
 # _b4_define_flag_if($1, $2, FLAG)
 # --------------------------------
 # Work around the impossibility to define macros inside macros,
-# because issuing `[$1]' is not possible in M4.  GNU M4 should provide
+# because issuing '[$1]' is not possible in M4.  GNU M4 should provide
 # $$1 a la M5/TeX.
 m4_define([_b4_define_flag_if],
 [m4_if([$1$2], $[1]$[2], [],
@@ -772,8 +772,8 @@ m4_define([b4_percent_define_default],
 # b4_percent_define_if_define(NAME, [VARIABLE = NAME])
 # ----------------------------------------------------
 # Define b4_NAME_if that executes its $1 or $2 depending whether
-# VARIABLE was %defined.  The characters `.' and `-' in VARIABLE are mapped
-# to `_'.
+# VARIABLE was %defined.  The characters '.' and `-' in VARIABLE are mapped
+# to '_'.
 m4_define([b4_percent_define_if_define_],
 [m4_define(m4_bpatsubst([b4_$1_if], [[-.]], [_]),
            [b4_percent_define_flag_if(m4_default([$2], [$1]),

data/c++.m4

@@ -54,8 +54,8 @@ b4_percent_define_default([[define_location_comparison]],
 m4_define([b4_namespace_ref], [b4_percent_define_get([[api.namespace]])])
 
 
-# Don't permit an empty b4_namespace_ref.  Any `::parser::foo' appended to it
-# would compile as an absolute reference with `parser' in the global namespace.
+# Don't permit an empty b4_namespace_ref.  Any '::parser::foo' appended to it
+# would compile as an absolute reference with 'parser' in the global namespace.
 # b4_namespace_open would open an anonymous namespace and thus establish
 # internal linkage.  This would compile.  However, it's cryptic, and internal
 # linkage for the parser would be specified in all translation units that

data/c.m4

@@ -150,7 +150,7 @@ m4_popdef([$1])dnl
 
 # b4_parse_param_use([VAL], [LOC])
 # --------------------------------
-# `YYUSE' VAL, LOC if locations are enabled, and all the parse-params.
+# 'YYUSE' VAL, LOC if locations are enabled, and all the parse-params.
 m4_define([b4_parse_param_use],
 [m4_ifvaln([$1], [  YYUSE ([$1]);])dnl
 b4_locations_if([m4_ifvaln([$2], [  YYUSE ([$2]);])])dnl
@@ -182,7 +182,7 @@ m4_define([b4_int_type],
 # b4_int_type_for(NAME)
 # ---------------------
 # Return the smallest int type able to handle numbers ranging from
-# `NAME_min' to `NAME_max' (included).
+# 'NAME_min' to 'NAME_max' (included).
 m4_define([b4_int_type_for],
 [b4_int_type($1_min, $1_max)])
 

data/java.m4

@@ -103,7 +103,7 @@ m4_define([b4_int_type],
 # b4_int_type_for(NAME)
 # ---------------------
 # Return the smallest int type able to handle numbers ranging from
-# `NAME_min' to `NAME_max' (included).
+# 'NAME_min' to 'NAME_max' (included).
 m4_define([b4_int_type_for],
 [b4_int_type($1_min, $1_max)])
 

data/lalr1.cc

@@ -824,7 +824,7 @@ b4_dollar_popdef])[]dnl
        variants.  */
     b4_symbol_variant([[yyr1_@{yyn@}]], [yylhs.value], [build])],[
     /* If YYLEN is nonzero, implement the default value of the action:
-       `$$ = $1'.  Otherwise, use the top of the stack.
+       '$$ = $1'.  Otherwise, use the top of the stack.
 
        Otherwise, the following line sets YYLHS.VALUE to garbage.
        This behavior is undocumented and Bison

data/lalr1.java

@@ -375,7 +375,7 @@ b4_lexer_if([[
     ]b4_locations_if([b4_location_type[ yyloc = yylloc (yystack, yylen);]])[
 
     /* If YYLEN is nonzero, implement the default value of the action:
-       `$$ = $1'.  Otherwise, use the top of the stack.
+       '$$ = $1'.  Otherwise, use the top of the stack.
 
        Otherwise, the following line sets YYVAL to garbage.
        This behavior is undocumented and Bison

data/yacc.c

@@ -223,9 +223,9 @@ m4_define([b4_declare_parser_state_variables], [b4_pure_if([[
     int yyerrstatus;
 
     /* The stacks and their tools:
-       `yyss': related to states.
-       `yyvs': related to semantic values.]b4_locations_if([[
-       `yyls': related to locations.]])[
+       'yyss': related to states.
+       'yyvs': related to semantic values.]b4_locations_if([[
+       'yyls': related to locations.]])[
 
        Refer to the stacks through separate pointers, to allow yyoverflow
        to reallocate them elsewhere.  */
@@ -468,7 +468,7 @@ b4_push_if([], [b4_lac_if([], [[
 # endif]])])[
 
 # ifdef YYSTACK_ALLOC
-   /* Pacify GCC's `empty if-body' warning.  */
+   /* Pacify GCC's 'empty if-body' warning.  */
 #  define YYSTACK_FREE(Ptr) do { /* empty */; } while (0)
 #  ifndef YYSTACK_ALLOC_MAXIMUM
     /* The OS might guarantee only one guard page at the bottom of the stack,
@@ -1654,7 +1654,7 @@ yyreduce:
   yylen = yyr2[yyn];
 
   /* If YYLEN is nonzero, implement the default value of the action:
-     `$$ = $1'.
+     '$$ = $1'.
 
      Otherwise, the following line sets YYVAL to garbage.
      This behavior is undocumented and Bison
@@ -1702,7 +1702,7 @@ yyreduce:
   *++yyvsp = yyval;]b4_locations_if([
   *++yylsp = yyloc;])[
 
-  /* Now `shift' the result of the reduction.  Determine what state
+  /* Now 'shift' the result of the reduction.  Determine what state
      that goes to, based on the state we popped back to and the rule
      number reduced by.  */