Refactor the feature detection section of _build_ffi.py to be more Pythonic.
Add detection of FIPS and RSA blinding. Don't enable RSA blinding if FIPS is
enabled. Full-fledged FIPS checks for other features are not included; this just
helps with RSA blinding, for now. Use this to determine if wc_RsaSetRNG is
available.
Change the various *_ENABLED variables to have extern, since they're
declared in a header and initialized in a source file.
Add a missing include of pwdbased.h to provide the declaration of wc_PBKDF2.
The changes affecting wc_RsaSetRNG should resolve ZD 12535.
The changes affecting wc_RsaSetRNG should resolve ZD 12535.