[DebugInfo] Changed DIBuilder::createCompileUnit() to take DIFile instead of...

[DebugInfo] Changed DIBuilder::createCompileUnit() to take DIFile instead of FileName and Directory.
This way it will be easier to expand DIFile (e.g., to contain checksum) without the need to modify the createCompileUnit() API.

Reviewers: cfe-commits, rnk

Differential Revision: https://reviews.llvm.org/D27763

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289701 91177308-0d34-0410-b5e6-96231b3b80d8