Remove empty std::type_info destructor.

This is provided by libcxxabi and there are actually 3 different
destructors, not just this one, so let things pick up libcxxabi correctly.
do not warn on missing emscripten_ functions
testcase for issue #2244
fix caching of asm const strings; fixes #2253
Merge pull request #2236 from waywardmonkeys/remove-invalid-type-info-destructor

Remove empty std::type_info destructor.
Merge remote-tracking branch 'upstream/incoming' into incoming