Emit personality function and Dwarf EH data for Win64 SEH.

Emit personality function and Dwarf EH data for Win64 SEH.

Obviously the personality function should be emitted as language handler
instead of the hard coded _GCC_specific_handler. The language specific
data must be placed after the unwind information therefore it must not
be emitted into a separate section.

Reviewed by Charles Davis and Nico Rieck.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185761 91177308-0d34-0410-b5e6-96231b3b80d8