fetching the selected text.

Bug: 2950652

Some refinements to correction behavior, such as retaining the tap-to-save
when in correction mode.

Use reflection to access the new InputConnection APIs with fallbacks, in case
we run on older OS versions.

Some refactoring to separate lookup for voice alternatives and typed alternatives.

Change-Id: I7c4178bf7e6b47ee274c49fa7a694f8c2d50cea7