Support more than two keys for compose

[GoogleCodeExporter]

Feature suggestion:

Simplest algorithm would be to search for an exact match, and use it if one is 
found, and if not, do the error sound / leave compose mode if there are no 
prefix matches either.

Avoiding collisions [a compose "ab" and "abc" for example] would simply be done 
by not defining any with collisions [maybe with a warning in the edit window], 
rather than doing anything clever like a delay to wait to see if they're going 
to type "c"

Original issue reported on code.google.com by [email protected] on 16 Feb 2011 at 4:49