Make unistr.h compile with -Werror and gcc4.6

BUG=87490
TEST=icu builds with -Werror and gcc 4.6

Original Review: http://codereview.chromium.org/8120001
CL by pph34r@gmail.com

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/icu46@106776 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
3 files changed