New JIT Feature

Folks,

I got tired of trying to figure out how to use Makefile.JIT and modify
it over time, so there is now a new "LLVMLIBS=JIT" feature in the
makefile system. See http://llvm.cs.uiuc.edu/docs/MakefileGuide.html#JIT
for the details.

This feature was aimed at solving the "can't link symbols starting with
two underscores" problem that occurred on PPC recently. The necessary
-ldopen self flag is now passed when building any JIT tool to ensure
symbols are resolved to the executable as well.

Could the PPC JIT folks update, rebuild lli and let me know if this
makefile change plus the usage of DynamicLibrary fixes the problem?

Thanks,

Reid.