[CallGraph] Take into accound calls that aren't within any function bodies.

This patch improves Clang call graph analysis by adding in expressions
that are not found in regular function bodies, such as default arguments
or member initializers.

Patch by Joshua Cranmer!

Differential Revision: https://reviews.llvm.org/D65453

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@369321 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed