when logging LatinIME.onUpdateSelection(), now include the current word and
preceding word. no escaping of the word is performed; this is temporary
until the output format is cleaned up.
also fix EditingUtils.getWordRangeAtCursor to support supplementary
UTF-16 characters.
Bug: 6188932
Change-Id: If4612a2627537d5d8bb2f9585a3ad1b4e56c2e26
