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!

src/asm/symbol.c

@@ -570,8 +570,6 @@ static inline char const *removeLeadingZeros(char const *ptr)
  */
 void sym_Init(void)
 {
-	macro_Init();
-
 	for (int32_t i = 0; i < HASHSIZE; i++)
 		tHashedSymbols[i] = NULL;