Mark not unmapping macro-containing files as okay

There isn't really a better alternative.
Making several mappings instead requires too much bookkeeping.

src/asm/lexer.c

@@ -2007,7 +2007,6 @@ void lexer_CaptureMacroBody(char **capture, size_t *size)
 
 	/* If the file is `mmap`ed, we need not to unmap it to keep access to the macro */
 	if (lexerState->isMmapped)
-		/* FIXME: this is godawful, but RGBASM doesn't even clean up anything anyways. */
 		lexerState->isReferenced = true;
 
 	/*