Clang-interpreter and JIT on Win32/MSVC

Hello,

In clang-interpreter example JIT (ExecutionEngine::JITCtor) is not
initialized, making program always fail with "unable to make execution
engine: JIT has not been linked in."
Adding #include "llvm/ExecutionEngine/JIT.h" to
clang-interpreter:main.cpp solves the problem (based on a comment in
llvm/ExecutionEngine/JIT.h stating "This file forces the JIT to link
in on certain operating systems (Windows))

Cheers,
Dean

Index: examples/clang-interpreter/main.cpp

r141324; thanks for the patch!

-Eli