[PATCH] Generate SEH unwinding info on Win64

[Aleksei]

I was wrong with example above. Looks like the only problem is sorting and sometimes overlapping ranges of Function start & end. For example, in cases when exist two or more .text sections there is no way at all to sort function starts  (in one .pdata section)
I think, solution is to create one .pdata (and maybe .xdata) for each exception info as MS VC compiler do

http://reviews.llvm.org/D4081