The C++ interop modules require C++ support. Explicitly require C++ as
a feature when building these modules. This has no impact on the
changes as all the tests enable C++ already.
This adds support to `ClangImporter` to import C++ member function operators as static methods into Swift, which is part of SR-12748.
The left-hand-side operand, which gets passed as the `this` pointer to the C++ function is represented as an additional first parameter in the Swift method. It gets mapped back in SILGen.
Two of the tests are disabled on Windows because we can't yet call member functions correctly on Windows (SR-13129).
Add a test to verify that C++ out-of-line operator functions are imported correctly.
Includes fixes for armv7 and arm64.
This is part of addressing SR-12748.
