[Python-Dev] Compact GC Header

[INADA Naoki]

Hi, all.

I hacked GC module and managed to slim PyGC_Head down from 3 words to 2
words.
It passes test suite, while some comments and code cleanup is needed before
merge.

* https://bugs.python.org/issue33597
* https://github.com/python/cpython/pull/7043

I want to merge it after 3.7.0rc1 and buildbots are stable, if Antoine or
other GC expert accept it.

I estimate it reduces 5% memory usage (RSS) and negligible performance
difference.
If someone interested in it, please test and benchmark it on GC heavy
application.

Regards,

-- 
INADA Naoki  <songofacandy at gmail.com>