bpo-35177, Python-ast.h: Fix "Yield" compiler warning (GH-10664)

Partially revert commit 5f2df88b63e50d23914e97ec778861a52abdeaad:
add "#undef Yield" to .c files after including Python-ast.h.

Fix the warning:

    winbase.h(102): warning C4005: 'Yield': macro redefinition
8 files changed