Add "-encoding UTF-8" option to javadoc.

This fixed docs build on Mac OS X 10.9 with Java 7.
Change-Id: I91e224456c9e6c43dbf13d691c3b37d21f94b0f3
Merge "Add "-encoding UTF-8" option to javadoc."
Merge Android Master.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>