Adding a callback mechanism to allow users of google.glog to provide

Adding a callback mechanism to allow users of google.glog to provide
their own implementation of  OpenObjectFileContainingPcAndGetStartAddress.

GTTF: Make stack trace symbolization code recognize more symbols.
One example is __libc_start_main (easy to check), there may be more.

Include the correct elf header on OpenBSD and Android.

Fix Coverity NO_EFFECT defect. Comparing unsigned greater than or equal zero is always true.

git-svn-id: https://google-glog.googlecode.com/svn/trunk@140 eb4d4688-79bd-11dd-afb4-1d65580434c0