Cherry-pick two upstream patches to the ICU regex engine

The patches for the following upstream two bugs are cherry-picked:

  http://bugs.icu-project.org/trac/ticket/11369
  http://bugs.icu-project.org/trac/ticket/11370


BUG=422824,430353
TEST=See the bugs.
TBR=mbarbella

Review URL: https://codereview.chromium.org/732743002

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/icu52@292943 4ff67af0-8c30-449e-8e8b-ad334ec8d88c