The duplicate definition works fine in environments where the inline
definition becomes a weak symbol in the object file, but if it gets
generated as a regular definition, the duplicate definition causes link
problems.
In most call sites the return value could easily be made const, which
gives both the reader and the compiler a bit more certainty about the code's
intentions. In theory this may help performance, but it's mainly for clarity.
The comments are based on reverse-engineering, and the unit tests are based
on the comments. It's possible that some of what's in there is not essential,
in which case, don't feel bad about changing it!
I left a third identical definition in place, though I updated it with my
changes to avoid creeping divergence, and noted the duplication in a comment.
It would be nice to get rid of this definition as well, but it'd introduce
headers from the main Moses tree into biconcor, which may be against policy.
