The new 'munge' module performs transformations on the source code.
It uses the AST (abstract syntax tree) representation of Python code
to recognize some idioms such as `if STATIC_TYPING:` and transforms
them into alternatives that have zero overhead in mpy-compiled files
(e.g., `if STATIC_TYPING:` is transformed into `if 0:`, which is eliminated
at compile time due to mpy-cross constant-propagation and dead branch
elimination)
The code assumes the input file is black-formatted. In particular, it
would malfunction if an if-statement and its body are on the same line:
`if STATIC_TYPING: print("boo")` would be incorrectly munged.
