[PATCH] Generate SEH unwinding info on Win64

[NAKAMURA Takumi]

I met entire JITTests.exe and lli.exe (and clang-interpreter) got broken, not only MultiJitTest.JitPool.

  Command 0 Stderr:
  pseudo instructions should be removed before code emission
  
  UNREACHABLE executed at C:\bb-win7\msbuild-llvmclang-x64-msc17-DA\llvm-project\llvm\lib\Target\X86\X86CodeEmitter.cpp:1106!

FYI,
mingw x64 Release+Asserts http://bb.pgr.jp/builders/ninja-clang-x64-mingw64-RA/builds/3572
msc17 x64 Debug+Asserts http://bb.pgr.jp/builders/msbuild-llvmclang-x64-msc17-DA/builds/731

I could help investigating if you couldn't reproduce failures.

http://reviews.llvm.org/D4081