Reland "[clang-repl] Adapt to the recent dylib-related changes in ORC."

Original commit message:"

ORC splits into separate dylibs symbols coming from the process and symbols
materialized in the Jit. This patch adapts intent of the existing interface and
adds a regression test to make sure both Jit'd and compiled symbols can be found.

Differential revision: https://reviews.llvm.org/D159115
"

This patch disables the test statement on windows as it seems we might have a
bug in the way we model dllimports.