Format closing braces when reformatting the line containing the opening brace.

This required a couple of yaks to be shaved:
1. MatchingOpeningBlockLineIndex was misused to also store the
   closing index; instead, use a second variable, as this doesn't
   work correctly for "} else {".
2. We needed to change the API of AffectedRangeManager to not
   use iterators; we always passed in begin / end for the whole
   container before, so there was no mismatch in generality.
3. We need an extra check to discontinue formatting at the top
   level, as we now sometimes change the indent of the closing
   brace, but want to bail out immediately afterwards, for
   example:
     void f() {
       if (a) {
     }
     void g();
   Previously:
     void f() {
       if (a) {
     }
     void g();
   Now:
     void f() {
       if (a) {
       }
     void g();

Differential Revision: https://reviews.llvm.org/D45726

llvm-svn: 330573