Merge branch 'session-id' into 'master'

m4/ax_python_devel.m4

src/mod_sso/session.c

src/sso/Makefile.am

src/sso/base64.h

src/sso/sso.c

src/sso/sso.h

src/sso/test/fuzz.sh

src/sso/test/fuzz_serialized.c

src/sso/test/fuzz_signed.c

src/sso/test/sso_unittest.cc