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.

Notes:
I'm not sure about the changes to test.py because it end up crashing with:
.libgccjit.so: internal compiler error: Segmentation fault
0x7fad42a2a0e6 crash_signal
        ../../src/gcc/toplev.c:336
0x7fad426c33c5 gcc::jit::function::add_conditional(gcc::jit::location*, gcc::jit::rvalue*, gcc::jit::label*, gcc::jit::label*)
        ../../src/gcc/jit/internal-api.c:944
0x7fad436a04ba __pyx_pf_6gccjit_8Function_8add_conditional
        /home/simon/projects/pygccjit/gccjit.c:3795
0x7fad436a04ba __pyx_pw_6gccjit_8Function_9add_conditional
        /home/simon/projects/pygccjit/gccjit.c:3766
0x7fad4369f1d8 __pyx_f_6gccjit__c_callback
        /home/simon/projects/pygccjit/gccjit.c:956
0x7fad426c2485 gcc::jit::context::invoke_code_factory()
        ../../src/gcc/jit/internal-api.c:1345

(I'm using Python3.3)