Make fast_parse able to parse real-world machine-generated code (#2766)

This is not changing the recursive nature of the visitor so it's effectively
a workaround.  However, this lets the parser deal with actual code in the wild,
such as `idnadata.py`.

Author: ambv

mypy/main.py

@@ -35,6 +35,7 @@ def main(script_path: str) -> None:
         bin_dir = find_bin_directory(script_path)
     else:
         bin_dir = None
+    sys.setrecursionlimit(2 ** 14)
     sources, options = process_options(sys.argv[1:])
     serious = False
     try: