tools: split out Win64EHDumper from COFFDumper

Move the implementation of the Win64 EH printer from the COFFDumper into its own
class.  This is in preparation for adding support to print ARM EH information.
The only real change here is in printUnwindInfo where we now lambda lift the
implicit this parameter for the resolveFunction.  Also setup the printing to
handle ARM.  This now has set the stage to introduce ARM EH printing.

llvm-svn: 209606