yum -C instead of --cacheonly

The `--cacheonly` long option isn't available in RHEL5's yum version.
The equivalent `-C` is available, however, in the older and newer
versions.
Don't require check test harness

We use check [1] as one of our testing harnesses.  RHEL5 doesn't provide
a new enough version of check for our purposes, though.  We can build
and install a newer version using Buzzy, but not until Buzzy is built:
a dastardly Catch-22.  So now we make all of the buzzy tests optional.
This lets us bootstrap and install a version of Buzzy, which we can then
use to build and install a newer version of check, which we can then use
to go back and run the Buzzy tests.

[1] http://check.sourceforge.net/
Fix uninitialized value warnings on RHEL5
Update to latest libcork
Handle multiple installed RPMs

RPM lets you install multiple copies of the same package, targeted at
different architectures.  (To let you install both 32-bit and 64-bit
libraries on a 64-bit system, for instance.)  This means that our
version parser needs to be a bit smarter, since there might be multiple
version strings to parse from the output of `rpm -q`.
Merge branch 'feature/rhel5' into develop

* feature/rhel5:
  Handle multiple installed RPMs
  Update to latest libcork
  Fix uninitialized value warnings on RHEL5
  Don't require check test harness
  yum -C instead of --cacheonly