Pass words as int[] to the native code.

We need to get the bigrams during the call to getSuggestions for
bug#6313806. We already give an int[] to getSuggestions and we
wanted to get rid of char[]'s anyway because it doesn't work with
surrogate pairs, so here we go.

Bug: 6313806
Change-Id: I56ce99f1db6b3302cdf42f0527343bded837091e