clang-apply-replacements: Add code formatting functionality

The tool now supports a collection of arguments to turn on and provide settings
for the formatting of code affected by applying replacements:
* --format turns on formatting (default style is LLVM)
* --style controls code style settings
* --style-config allows one to explicitly indicate where a style config file
  lives.

The libclangApplyReplacements interface has a new function to turn Replacements
into Ranges to be used with tooling::reformat().