On windows, set "LANDMARK" definition to ensure proper lookup of library

By not doing so, LANDMARK will default to "lib\\os.py" as specified
in getpathp.c.
On windows, InlineFunctionExpension /Ob1 flags is expected.

If not, build will fail with link error. Grepping the different vcproj
file in the PCbuild folder also indicate that this property is on.
Fix build error setting --enable-auto-import flag only for MINGW
Fix build error preventing mingw _ctypes module from being built on MSVC

Todo: re-enable the build of _ctypes for windows build
Fix windows build of pyexpat/elementtree passing the expected definition
By design, some module are expected to be built-in on windows.

These modules belongs to the "pythoncore" project when built on windows
and are not designed to be externally built. By not doing so,
link error occurs because of undefined symbols.
On windows, do not pass PLAFORM to 'getplatform.c' - value hardcoded in pyconfig.h
Fix indent - Use 4 spaces and no tabs in CMake files.
On windows, building as static isn't yet supported.
Set PY_PLATFORM CMake variable on all platform.

It is used to set the default "PYTHONPATH" in libpython/CMakeLists.txt