Minor cleanups to Java dependency build process

Minor cleanups to Java dependency build process

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.

Signed-off-by: Dan Scott <dan@coffeecode.net>