recognize -std=gnu11 and treat it the same as -std=c11

Author: pskocik

libtcc.c

@@ -1977,7 +1977,7 @@ PUB_FUNC int tcc_parse_args(TCCState *s, int *pargc, char ***pargv, int optind)
             s->static_link = 1;
             break;
         case TCC_OPTION_std:
-            if (strcmp(optarg, "=c11") == 0)
+            if (strcmp(optarg, "=c11") == 0 || strcmp(optarg, "=gnu11") == 0)
                 s->cversion = 201112;
             break;
         case TCC_OPTION_shared:

tcc.c

@@ -33,8 +33,8 @@ static const char help[] =
     "  -o outfile   set output filename\n"
     "  -run         run compiled source\n"
     "  -fflag       set or reset (with 'no-' prefix) 'flag' (see tcc -hh)\n"
-    "  -std=c99     Conform to the ISO 1999 C standard (default).\n"
-    "  -std=c11     Conform to the ISO 2011 C standard.\n"
+    "  -std=(c99|gnu99)     Conform to the ISO 1999 C standard (default).\n"
+    "  -std=(c11|gnu11)    Conform to the ISO 2011 C standard.\n"
     "  -Wwarning    set or reset (with 'no-' prefix) 'warning' (see tcc -hh)\n"
     "  -w           disable all warnings\n"
     "  -v --version show version\n"