<rdar://problem/13415737>

Fixing a bug where LLDB was not handling correctly CFStrings that have an explicit length but no NULL terminator
The data formatter was showing garbled data as part of the summary
The fix is to explicitly figure out the explicit length if we need to (bitfields tell us when that is the case) and use that as a size delimiter



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@178577 91177308-0d34-0410-b5e6-96231b3b80d8