Added a new API to the IRInterpreter (the old API
will be gone soon!) that lets it interpret a function
using just an llvm::Module, an llvm::Function, and a
MemoryMap.

Also added an API to IRExecutionUnit to get at its
llvm::Function, so that the IRInterpreter can work
with it.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@179704 91177308-0d34-0410-b5e6-96231b3b80d8