Various fixes to allow regression tests to pass on Linux
Added missing include files for compiling with MSVC
Added CMake files for libffi
Various fixes for building on Windows with MSVC
Don't use 16 byte aligned stack for WIN32

This fixes a crash when accessing __stdcall functions in Python ctypes.
Partial revert of commit b641713ea1536e1f8e4da32c936f21fb8e5329a9

Tests have been kept, but libffi_msvc files removed.
Handle MinGW __stdcall mangling
Don't assume gethostbyaddr_r exists if gethostbyname_r does

This fixes build on Android.
Install pyconfig.h on Windows too
Enable building libffi for arm
Fix bug in check for HAVE_STAT_TV_NSEC2
Don't assume existence of pthread library in configure checks

This fixes build on Android, which has no separate pthread library.