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.
Explain what LLVM is for new users
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.
Adding @dandv
Merge branch 'patch-2' of github.com:dandv/emscripten into incoming

Conflicts:
	AUTHORS
Merge branch 'patch-1' of github.com:dandv/emscripten into incoming

Conflicts:
	README.markdown
1.14.0
--emit-symbol-map option
add testcase for use of call outputs to absolute targets
improve testcase
play-ttd optiization tricks