[TRE-general] function names

[William J Poser]

I wonder if it wouldn't be a good idea to name all of the
public functions with a prefix such as "tre_" that would
make them unique to the library? That way, failure to link
to libtre would show up at link time rather than as run time
bugs. For backwards compatibility there could be a flag
defaulting to FALSE that would control the use of the prefixless
names.

Bill