Revamp macro arg system

This should significantly improve performance: on pokecrystal builds, perf
reported as much CPU time spent on `yyparse` as on `sym_UseNewMacroArgs`
Measurements show ~6 seconds of improvement on that codebase.

This also fixes #321, as a bonus, due to saner management!

include/helpers.h

@@ -27,4 +27,8 @@
 	#define DEVELOP 0
 #endif
 
+/* Macros for stringification */
+#define STR(x) #x
+#define EXPAND_AND_STR(x) STR(x)
+
 #endif /* HELPERS_H */