Create two variants of libstagefright_mpeg2support library

A flag ENABLE_CRYPTO is defined to selectively enable crypto dependencies
for libstagefright_mpeg2support

A library libtagefright_mpeg2support_nocrypto is created that has all the
crypto dependencies removed and is made available to apex

Test: Build libtagefright_mpeg2support_nocrypto
Test: Build libstagefright_mpeg2support
Bug: 159070321

Change-Id: Id4a9fb446181fd04b9fce1ed8a27f5b9862a3bc7