Fix a bug with single quotes

I14dd3815 special-cased single quotes at the start of a word, but
did not do so correctly - it would kill a composing word if entered
just after some punctuations.
The right test was not isCursorTouchingWord() but
mHasUncommittedTypedChars, which actually makes for a simpler
implementation.

Bug: 5648032
Change-Id: Icd21d213e0cad6da68cacfeb921502cd8dcfac95