[clang-diff] Move printing of matches and changes to clang-diff

Summary:
This also changes the output order of the changes. Now the matches are
printed in pre-order, intertwined with insertions, updates, and moves.
Deletions are printed afterwards.

Reviewers: arphaman

Subscribers: klimek

Differential Revision: https://reviews.llvm.org/D36179

llvm-svn: 311200