The clang and gcc autoloaders are not necessary any more to optain the system include paths. Due to the previous commit, the include paths are now correctly added by the clang driver. libclang always used internally the clang driver and never had problems finding the system include paths. We remove these options as incorrectly derived include paths can cause all kind of spurious problems. We now print the following message, if someone manually adds 'clang' or 'gcc' to the auto_user_options: 'gcc' in clang_auto_user_options is deprecated.
I didn't tested it with ultisnips but due to the similarity of the code, it should works. Some features were removed for now and may be reintroduced in the future.