Revert r320978 "No -fsanitize=function warning when calling noexcept function...

Revert r320978 "No -fsanitize=function warning when calling noexcept function through non-noexcept pointer in C++17"

At least <http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-android/
builds/6013/steps/annotate/logs/stdio> complains about
__ubsan::__ubsan_handle_function_type_mismatch_abort (compiler-rt
lib/ubsan/ubsan_handlers.cc) returning now despite being declared 'noreturn', so
looks like a different approach is needed for the function_type_mismatch check
to be called also in cases that may ultimately succeed.

llvm-svn: 320982