Remove the various get_*_type function and add get_type with enum arg

libgccjit.so commit 5de6c0a32cda8eb7838289b6ce240a093b59958a removed various
APIs for getting specific type objects which was replaced by a generic
"get_type" with an enum arg. Update Python API accordingly.
Merge pull request #1 from sfeltman/master

Remove the various get_*_type function and add get_type with enum arg