gabi++: Fix terminate / unexpected thread-safety.
David 'Digit' Turner authored
This patch makes all operations on terminate and unexpected
handlers properly thread-safe. This also marks the appropriate
functions as "noreturn".

+ Move internal <cxxabi.h> declarations to internal header
  src/cxxabi_defines.h

+ Add new <gabixx_config.h> header.

+ Move some exception-specific code to src/exception.cc

+ Rename __cxxabiv1::fatalError() to __gabixx::__fatal_error() in
  src/fatal_error.cc

+ Get rid of __cxa_thread_info.

Change-Id: If79bf0263cc5f0be1bbf782a7874125fd4923d17
7a9c3769