doc(cmake/osx10.8): add note regarding multi-thread support on OSX

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(util/memory): remove get_thread_allocated_memory, it used thread_local

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(tests/util): disable some tests that do not compile on OSX + Boost + MULTI_THREAD
fix(CMakeLists): remove -pthread flag when compiling using Boost on OSX

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(tests/util/memory): remove reference to deleted function

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>