python: Support the Assuan engine.
* lang/python/gpgme.i: Add typemaps for the Assuan protocol callbacks.
* lang/python/helpers.c (_pyme_assuan_{data,inquire,status}_cb): New
functions.
* lang/python/private.h (_pyme_assuan_{data,inquire,status}_cb): New
prototypes.
* lang/python/pyme/core.py (Context.assuan_transact): New method.
* lang/python/pyme/util.py (percent_escape): New function.
* lang/python/tests/Makefile.am (py_tests): Add new test.
* lang/python/tests/t-protocol-assuan.py: New file.- Signed-off-by: Justus Winter <justus@g10code.com>