Start documenting y_string.c
Start expanding the documentation for y_string.c a bit.
Suppress the doxygen warning about HTML output and the search engine.

It's getting tiresome.
Minor documentation fixes.
Tell doxygen to be quiet when there are no errors or warnings to report.
More documentation updates.

I'm staging this now because I found a bug reading the code here.
y_last_right() - fix the check for empty parameters.
More progress on getting the y_string.c documentation to show up in doxygen.
Fix some doxygen warnings.
Continue the quest to document y_string.c
Completing the y_string.c documentation.

As far as doxygen conversion is concerned, this ends the series for y_string.c
Now for the others ..
Enable the doxygen source browser for all files.
This gives a "go to the source code for this file" link at the top of each of the files.
Add a brief description to vugen.h
Add a brief description to y_string.c, start hiding internal-only code from the user.
Doxify the vugen.h top level comment.
Rename the y_string.c include protection #define in an attempt to figure out why vugen.h does not need \cond tags for that same thing.

The attempt failed, though. :(
Update the y_string.c copyright notice.