Portable Python script across Python version

In Python3, dict.items, dict.keys, dict.values, zip, map and filter no longer return lists, they create generator instead.

The portability patch consists in forcing an extra `list` call if the result is actually used as a list.
`map` are replaced by list comprehension and `filter` by filtered list comprehension.

Differential Revision: https://reviews.llvm.org/D55197

llvm-svn: 349501