While configure.ac still hardcodes the expected location of the Java
dependencies (JSON and Memcached classes), we can clean up some of the
lower-level challenges with the Java build.
* StAX and WSTX were rolled into the core Java environment long ago,
so there's no need to download them and even less need to verify
that the downloaded version exist.
* The Memcached class is now up to 2.0.1, per deps.sh, but the deps.inc
file was pointing at 1.5.1.
* Speaking of the deps.inc file, nothing seems to use it; delete it.
* The Makefile was dying because the variables for the Memcached and
JSON classes weren't defined. Define those at the top of the Makefile.