always instantiate exceptions directly when raising them, fix Py3 crash when an exception type does not create an exception instance (works in Py2, although not in PyPy)

prevent utility code of overloaded function entries from accidentally being written to the output file

added safety assertion to prevent utility code from overwriting that of other entries with the same name

use proper module.m_free() way to run module cleanup code in Py3, way after running atexit functions etc.

moved utility code for registering the module cleanup function into Cython/Utility/ModuleSetupCode.c

fix compiler crash during type inference when calling Python method of C int variable (found in Py3 pyregr test_long.py)

Update docs/src/tutorial/caveats.rst

small grammar error/typo in doc