Use user's JVM on Linux without depending on RPATH

[Chris Hillery]

In Zorba 2.8, the util-jvm module specifically depended on OpenJDK 6.

In Zorba 2.9, we have improved this by (we believe) allowing the user to have other JVMs installed. However, in order to achieve this, we set the RPATH of libutil-jvm.so to point to a number of common locations for libjvm.so.

This is not the "Right Approach", but it is not clear what actually is. On Ubuntu there does not seem to be an /etc/alternatives entry for libjvm.so so we can't link against that. RPATH, however, is evidently strongly deprecated (Debian and Fedora packaging guidelines disallow it, from what I have read), so we really should come up with something else for Zorba 3.0.

Possibly we could use dlopen() at runtime to find libjvm.so, based on the location of the java executable (which can be traced via symlinks from the PATH)?