Closed #16886: test_dictcomps no longer depends on dict order
#16886: merge with 3.2
#16886: merge with 3.3
Use unittest.main() in 3.3 and greater
merge with 3.3
Issue #11729: Backport commit bff052d9 from libffi upstream in order to fix
a ctypes build failure with clang.
Merge 3.3.