Split DescribeAddressIfGlobal between a function that gets all the...

Split DescribeAddressIfGlobal between a function that gets all the information, and one that prints it.

Summary:
Replacement for part of D23518
This deals with global variable addresses.

(This commit is written on top of D23605, but can be applied by itself)

Reviewers: kcc, samsonov

Subscribers: kubabrecka, llvm-commits

Differential Revision: https://reviews.llvm.org/D23607

llvm-svn: 278959