[analyzer; new edges] Include a top-level function entry edge while optimizing.

Although we don't want to show a function entry edge for a top-level path,
having it makes optimizing edges a little more uniform.

This does not affect any edges now, but will affect context edge generation
(next commit).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183158 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed