Expand toys.optargs to 64 bits so people adding more options to ls don't run out.

Keep the low 32 bits of FLAG_x constants as 32 bit numbers so that at least
on little endian platforms it's still normal 32 bit math outside of lib/args.c.
diff --git a/toys.h b/toys.h
index 9c33ff2..688d558 100644
--- a/toys.h
+++ b/toys.h
@@ -122,7 +122,7 @@
   struct toy_list *which;  // Which entry in toy_list is this one?
   char **argv;             // Original command line arguments
   char **optargs;          // Arguments left over from get_optflags()
-  unsigned optflags;       // Command line option flags from get_optflags()
+  unsigned long long optflags; // Command line option flags from get_optflags()
   int exitval;             // Value error_exit feeds to exit()
   int optc;                // Count of optargs
   int old_umask;           // Old umask preserved by TOYFLAG_UMASK