i965: improve debug logging

i965: improve debug logging

Looking for memory leaks that were causing crashes in my environment
in a situation where valgrind would not work, I ended up improving
the i965 debug traces so I could better see where the memory was
being allocated and where it was going, in the regions and miptrees
code, and in the state caches.  These traces were specific enough
that external scripts could determine what elements were not being
released, and where the memory leaks were.

I also ended up creating my own backtrace code in intel_regions.c,
to determine exactly where regions were being allocated and for what,
since valgrind wasn't working.  Because it was useful, I left it in,
but disabled and compiled out.  It can be activated by changing a flag
at the top of the file.