Bug 1041886 - Break out Linux sandbox logging into its own header. r=kang
Bug 1041886 - Separate Linux sandbox code into its own shared library. r=kang r=glandium

This creates libmozsandbox.so on builds that use sandboxing
(MOZ_CONTENT_SANDBOX or MOZ_GMP_SANDBOX).

The unavoidably libxul-dependent parts, for invoking the crash reporter
and printing the JS context, are separated into glue/SandboxCrash.cpp
and invoked via a callback.
Bug 1054616 - Clean up logging-related shims for Linux sandboxing. r=kang