Tokenize whilst parsing rather than storing every token of a file first

src/checker.cpp

@@ -7803,9 +7803,7 @@ gb_internal void check_parsed_files(Checker *c) {
 			token.pos.column  = 1;
 			if (s->pkg->files.count > 0) {
 				AstFile *f = s->pkg->files[0];
-				if (f->tokens.count > 0) {
-					token = f->tokens[0];
-				}
+				token = f->first_token;
 			}
 
 			error(token, "Undefined entry point procedure 'main'");