avoid accidental duplication of cached Python integer constants when using numbers in different notations

try fixing test failures in int_literals.pyx by removing dependency on Py2/3 specific 'L' postfix of long objects

discard lots of useless code and overhead from try-finally statements that don't need to handle Python exceptions (including C-only with-blocks)

fix problematic constant folding condition in cascaded comparisons (even though it likely doesn't work anyway)

prevent compile time constant folding of non-portable string comparisons (e.g. between bytes and str)

avoid risk of stale pointers by looking up Cython types module on each request (shouldn't hurt much to do it a couple of times during module initialisation)

discard useless (PyObject*) casts from values of builtin types which are PyObject* internally anyway (saves lots of C code)

--HG--
extra : amend_source : 240f49031159777036e1e6a139b6d736f59de337

fix C compiler warning when checking int overflow for division by enum values on 32 bit systems (in case anyone cares...)

minor improvements in __Pyx_ArgTypeTest() and prevent it from raising C compiler warnings by inlining it