Bug 914253 patch 1 - Initial version of fix_linux_stack.py, based on slightly old version of fix_macosx_stack.py.  No review.

--HG--
rename : tools/rb/fix_macosx_stack.py => tools/rb/fix_linux_stack.py
Bug 914253 patch 2 - Pull opening comment from fix-linux-stack.pl.  No review.
Bug 914253 patch 3 - Implement separate debug info for fix_linux_stack.py, including the addition of support for .note.gnu.build-id sections that fix-linux-stack.pl did not support.  No review.
Bug 914253 patch 4 - Implement address adjustment for fix_linux_stack.py.  No review.
Bug 914253 patch 5 - Implement caching of addr2line results, like bug 812070 did for fix-linux-stack.pl.  No review.
Bug 914253 patch 6 - Linux stacks are lowercase hexidecimal (although this was temporarily not true due to bug 939610, which is probably when mccr8 started fix_linux_stack.py).  No review.