LibC: Expose various option variables for later usage

These variables are used by the dmidecode utility to parse the
commandline arguments that were specified by the user.

Userland/Libraries/LibC/getopt.h

@@ -41,6 +41,11 @@ struct option {
     int val;
 };
 
+extern int opterr;
+extern int optopt;
+extern int optind;
+extern int optreset;
+extern char* optarg;
 int getopt_long(int argc, char** argv, const char* short_options, const struct option* long_options, int* out_long_option_index);
 
 __END_DECLS