Kick JSON output for XML output.

Kick JSON output for XML output.

Apparently the owners of the tools we want to integrate with (eclipse in
this case) don't have JSON parsers.

The output now is:
<replacements>
<replacement offset='2' length='3'>  </replacement>
...
</replacements>

Kicking JSON for now - it's easy enough to get back in when we need it.

FIXME: once we find this useful enough, we might want to add it as
free-standing functions to tooling.

llvm-svn: 174497