MAINT: Update the C-API hash in cversions.txt.

The new annotations caused the api hash to change.
MAINT: Delete code_generators/cversions.py in its old location.
MAINT: Add NPY_1_9_API_VERSION to numpyconfig.h.

Defined to the same value as NPY_1_8_API_VERSION as there have
been no deprecated macros or functions in the include files.