Support underscore (_) in VFormat arg name

This is needed for the limits check in the translator menu.

This commit is part of rewritten history of the localization branch.
The original (unsquashed) commit history can be found here:
https://github.com/Dav999-v/VVVVVV/tree/localization-orig

desktop_version/src/VFormat.c

@@ -245,7 +245,8 @@ void vformat_cb_valist(
                 trim_whitespace(&arg_name, &arg_name_len);
                 trim_whitespace(&arg_type, &arg_type_len);
 
-                match = (arg_name_len == name_len && SDL_memcmp(arg_name, name, name_len) == 0);
+                match = (arg_name_len == name_len && SDL_memcmp(arg_name, name, name_len) == 0)
+                     || (arg_name_len == 1 && arg_name[0] == '_');
 
                 if (arg_type_len == 3 && SDL_memcmp(arg_type, "int", 3) == 0)
                 {

desktop_version/src/VFormat.h

@@ -45,6 +45,9 @@
  *  - str   const char*
  *  - but   Controller button icon
  *
+ * Special case: if an argument name is a single underscore (_), it matches
+ * any name not found earlier in the list. This should normally not be needed.
+ *
  * Full example:
  *
  *  char buffer[100];