[WinEH] Teach AsmPrinter about funclets

[WinEH] Teach AsmPrinter about funclets

Summary:
Funclets have been turned into functions by the time they hit the object
file.  Make sure that they have decent names for the symbol table and
CFI directives explaining how to reason about their prologues.

Differential Revision: http://reviews.llvm.org/D13261

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248824 91177308-0d34-0410-b5e6-96231b3b80d8