Improve existing visualizers by:

- Properly displaying non null terminated StringRef.
- Auto expanding pointer types.
- Displaying real type names for PointerUnions.
- Using "size" and "capacity" across all containers.
- Simplifying code where possible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201004 91177308-0d34-0410-b5e6-96231b3b80d8