Bug 7377: printf checking fails to flag some undefined behavior

http://llvm.org/bugs/show_bug.cgi?id=7377

Updated format string highlighting and fixits to take advantage of the new CharSourceRange class.
- Change HighlightRange to allow highlighting whitespace only in a CharSourceRange (for warnings about the ' ' (space) flag)
- Change format specifier range helper function to allow for half-open ranges (+1 to end)
- Enabled previously failing tests (FIXMEs/XFAILs removed)
- Small fixes and additions to format string test cases

M       test/Sema/format-strings.c
M       test/Sema/format-strings-fixit.c
M       lib/Frontend/TextDiagnosticPrinter.cpp
M       lib/Sema/SemaChecking.cpp

llvm-svn: 106480