style: c: fix a few minor issues about indentation of cpp directives

* README-hacking.md: More about cpp.
* data/skeletons/c.m4, data/skeletons/yacc.c: Style changes.

NEWS

@@ -17,6 +17,12 @@ GNU Bison NEWS
   (2013-07-25), "%error-verbose" is deprecated in favor of "%define
   parse.error verbose".
 
+** Deprecated features
+
+  The YYPRINT macro, which works only with yacc.c and only for tokens, was
+  obsoleted long ago by %printer, introduced in Bison 1.50 (November 2002).
+  It is deprecated and its support will be removed eventually.
+
 ** New features
 
 *** Improved syntax error messages

README-hacking.md

@@ -57,6 +57,31 @@ Actually, Bison has legacy code that we should replace with gnulib modules
 ### Skeletons
 We try to use the "typical" coding style for each language.
 
+#### CPP
+We indent the CPP directives this way:
+
+```
+#if FOO
+# if BAR
+#  define BAZ
+# endif
+#endif
+```
+
+Don't indent with leading spaces in the skeletons (it's ok in the grammar
+files though, e.g., in `%code {...}` blocks).
+
+On occasions, use `cppi -c` to see where we stand.  We don't aim at full
+correctness: depending `-d`, some bits can be in the *.c file, or the *.h
+file within the double-inclusion cpp-guards.  In that case, favor the case
+of the *.h file, but don't waste time on this.
+
+Don't hesitate to leave a comment on the `#endif` (e.g., `#endif /* FOO
+*/`), especially for long blocks.
+
+There is no conistency on `! defined` vs. `!defined`.  The day gnulib
+decides, we'll follow them.
+
 #### C/C++
 Follow the GNU Coding Standards.
 

data/skeletons/c.m4

@@ -1002,7 +1002,7 @@ yy_location_print_ (FILE *yyo, YYLTYPE const * const yylocp)
 #  else
 #   define YY_LOCATION_PRINT(File, Loc) ((void) 0)
 #  endif
-#endif]],
+# endif /* !defined YY_LOCATION_PRINT */]],
 [[/* This macro is provided for backward compatibility. */
 # ifndef YY_LOCATION_PRINT
 #  define YY_LOCATION_PRINT(File, Loc) ((void) 0)

src/parse-gram.c

@@ -1014,7 +1014,7 @@ yy_location_print_ (FILE *yyo, YYLTYPE const * const yylocp)
 #  else
 #   define YY_LOCATION_PRINT(File, Loc) ((void) 0)
 #  endif
-#endif
+# endif /* !defined YY_LOCATION_PRINT */
 
 
 # define YY_SYMBOL_PRINT(Title, Type, Value, Location)                    \