yacc.c: instead of duplicating y.tab.h inside y.tac.c, include it.

This is already what glr.c and lalr1.cc do.

* data/yacc.c: here.

NEWS

@@ -2,6 +2,20 @@ GNU Bison NEWS
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
+** Future changes:
+
+  The next major release will drop support for generating parsers in K&R C,
+  and remove the definition of yystype (removal announced since Bison
+  1.875).
+
+** Changes in regular C parsers (yacc.c):
+
+*** The generated header is included
+
+  Instead of duplicating the content of the generated header (definition of
+  YYSTYPE, yyltype etc.), the generated parser now includes it, as was
+  already the case for GLR or C++ parsers.
+
 * Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
 
 ** Future changes:

data/glr.c

@@ -203,7 +203,7 @@ m4_if(b4_prefix, [yy], [],
 ]b4_null_define[
 
 ]b4_defines_if([[#include "@basename(]b4_spec_defines_file[@)"]],
-              [b4_shared_declarations])[
+               [b4_shared_declarations])[
 
 /* Enabling traces.  */
 #ifndef YYDEBUG

data/yacc.c

@@ -319,7 +319,8 @@ m4_if(b4_prefix, [yy], [],
 # define YYTOKEN_TABLE ]b4_token_table[
 #endif
 
-]b4_shared_declarations[
+]b4_defines_if([[#include "@basename(]b4_spec_defines_file[@)"]],
+               [b4_shared_declarations])[
 
 /* Copy the second part of user declarations.  */
 ]b4_user_post_prologue