Fix the inliner to always delete any edges from the external call node to

Fix the inliner to always delete any edges from the external call node to
a function being deleted.  Due to optimizations done while inlining, there
can be edges from the external call node to a function node that were not
apparent any longer.

This fixes the compiler crash while compiling 175.vpr

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16399 91177308-0d34-0410-b5e6-96231b3b80d8