Recommit r281457 "Supports adding insertion around non-insertion replacements".

Summary:
Diff to r281457:
- added a test case `CalculateRangesOfInsertionAroundReplacement`.

Reviewers: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D24606

llvm-svn: 281891