maint: use STREQ/STRNEQ.

* doc/bison.texinfo: Space change.
	* src/system.h (STREQ, STRNEQ): New.
	* src/files.c, src/ielr.c, src/lalr.c, src/muscle-tab.c,
	* src/output.c, src/print.c, src/print_graph.c,
	* src/reader.c, src/scan-skel.l, src/tables.c,
	* src/uniqstr.c:
	Use them.
	* src/scan-gram.l: Do not use streq.h, use system.h's STREQ.
	* cfg.mk: The documentation is an exception.

src/lalr.c

@@ -372,8 +372,7 @@ initialize_LA (void)
   {
     char *default_reductions =
       muscle_percent_define_get ("lr.default-reductions");
-    default_reduction_only_for_accept =
-      0 == strcmp (default_reductions, "accepting");
+    default_reduction_only_for_accept = STREQ (default_reductions, "accepting");
     free (default_reductions);
   }