Fixes CMake warning about the symbol visibility policy CMP0063
caused by 3party libs that claim to support older CMake versions.
Updated expat build settings. We don't use DTD and general entities.
Signed-off-by: Alexander Borsuk <me@alex.bio>
expat_config.h is generated by CMake, but for XCode project we don't use CMake at the moment.
So the file, generated for Mac, is used there.
Signed-off-by: Alexander Borsuk <me@alex.bio>