[PATCH] Generate SEH unwinding info on Win64

[Keno Fischer]

I went and tried this out but ran into an assertion. This is odd because at that stage I wasn't actually using COFF, but rather ELF in memory for MCJIT. Maybe there's a check missing whether we are using COFF in addition to Win64? See below:


  Program: C:\mingw-builds\msys64\home\kfischer\julia\usr\bin\julia.exe
  File: C:/mingw-builds/msys64/home/kfischer/julia/deps/llvm-svn/lib/CodeGen/MachineInstr.cpp, Line 674
  
  Expression: (isImpReg || Op.isRegMask() || MCID->isVariadic() || OpNo < MCID->getNumOperands() || isMetaDataOp) && "Trying to add an operand to a machine instr that is already done!"

http://reviews.llvm.org/D4081