* data/c.m4 (b4_dirname): New.

(b4_syncline): Also output the location of its invocation (from
the skeleton).
(b4_user_action, b4_define_user_action, b4_user_actions)
(b4_user_initial_action, b4_user_post_prologue,	b4_user_start_header)
(b4_user_stype): New.
* data/yacc.c, data/glr.c, data/lalr1.cc, data/glr.cc: Use them.

data/glr.cc

@@ -90,8 +90,7 @@ m4_define([b4_yy_symbol_print_generate],
 
 # Declare yyerror.
 m4_append([b4_post_prologue],
-[/* Line __line__ of glr.cc.  */
-b4_syncline([@oline@], [@ofile@])
+[b4_syncline([@oline@], [@ofile@])
 
 b4_c_ansi_function_decl([yyerror],
     [static void],
@@ -102,8 +101,7 @@ b4_c_ansi_function_decl([yyerror],
 
 # Define yyerror.
 m4_append([b4_epilogue],
-[/* Line __line__ of glr.cc.  */
-b4_syncline([@oline@], [@ofile@])[
+[b4_syncline([@oline@], [@ofile@])[
 /*------------------.
 | Report an error.  |
 `------------------*/
@@ -237,10 +235,7 @@ namespace ]b4_namespace[
 
 ]m4_ifdef([b4_start_header],
 [[/* Copy the %start-header blocks.  */
-]b4_start_header])[]dnl
-
-[/* Line __line__ of glr.cc.  */
-]b4_syncline([@oline@], [@ofile@])[
+]b4_user_start_header])[
 
 #include "location.hh"
 
@@ -291,9 +286,7 @@ namespace ]b4_namespace[
 #ifndef YYSTYPE
 ]m4_ifdef([b4_stype],
 [    union semantic_type
-b4_stype
-/* Line __line__ of lalr1.cc.  */
-b4_syncline([@oline@], [@ofile@])
+b4_user_stype
 	;],
 [    typedef int semantic_type;])[
 #else