[ORC] Re-apply r321838 again with a workaround for a bug present in the libcxx

version being used on some of the green dragon builders (plus a clang-format).

Workaround: AsynchronousSymbolQuery and VSO want to work with
JITEvaluatedSymbols anyway, so just use them (instead of JITSymbol, which
happens to tickle the bug).

The libcxx bug being worked around was fixed in r276003, and there are plans to
update the offending builders.

llvm-svn: 322140