Pacify -DGNULIB_POSIXCHECK.

* bootstrap.conf (gnulib_modules): Add all modules suggested by
-DGNULIB_POSIXCHECK.
* src/files.c (file_name_split)
* src/getargs.c (getargs)
* src/location.c (boundary_set_from_string)
* src/output.c (token_definitions_output, output_skeleton)
* src/parse-gram.y (prologue_declaration)
* src/scan-gram.l (handle_syncline)
* src/symtab.c (symbol_new): Use mbschr and mbsrchr instead of
strchr and strrchr.  In the cases of command-line options, file
names, and thus locations, functionality may be improved.  In the
case of symbol names, there should be no functional difference as
all characters are ASCII, so the intended benefit is just warning
suppression.

src/parse-gram.c

@@ -1,4 +1,4 @@
-/* A Bison parser, made by GNU Bison 2.4.1.287-8f46.  */
+/* A Bison parser, made by GNU Bison 2.4.1.302-e8fa.  */
 
 /* Bison implementation for Yacc-like parsers in C
    
@@ -44,7 +44,7 @@
 #define YYBISON 1
 
 /* Bison version.  */
-#define YYBISON_VERSION "2.4.1.287-8f46"
+#define YYBISON_VERSION "2.4.1.302-e8fa"
 
 /* Skeleton name.  */
 #define YYSKELETON_NAME "yacc.c"
@@ -2410,7 +2410,7 @@ yyreduce:
 #line 311 "parse-gram.y"
     {
       char const *skeleton_user = (yyvsp[(2) - (2)].chars);
-      if (strchr (skeleton_user, '/'))
+      if (mbschr (skeleton_user, '/'))
         {
           size_t dir_length = strlen (current_file);
           char *skeleton_build;