Fix memory leak in harfbuzz.

This commit cherrypicks the following commit into the harfbuzz.old
repository, and also picks up a simple fix to the Tibetan shaper.

http://cgit.freedesktop.org/harfbuzz.old/commit/?id=3ab7b37bdebf0f8773493a1fee910b151c4de30f

It should fix some memory leaks observed with Arabic-family scripts.

Change-Id: I31ba3f619506e843b10360b733d36097aa22653a
4 files changed