XSB Src (SVN)-old

Added a note of documentation about something that confused me. No change to .xwam

Fixed typo-based bug in partial forest logging.

fixed a buglet in parser/auxilry that created the following problem:
compile(foobar,[xpp_on])
executed twice in the same xsb session would fail the second time.
Added a test for the above.
Also updated a lot of xwam files that weren't recompiled for some reason.

Added xsb_throw_error to allow more precise error messages than
obtained by the very general xsb_abort. Used it in biassert to better
categorize assert error messages. Perhaps other uses of xsb_abort
might be changed.

Exported xsb_sprint_variable so C programs can use it. (Asked by by MK).

Removed default assumption in setting CHARACTER_SET, now returning
error if unrecognized char-set.

Fixed bug introduced in returing strings, when added character sets.
Also added new better error reporting.

Minor change to fix a compiler warning on the mac.

Forgot to commit earlier.

Previous commit had bug. Set ep of old usermod psc record only if it
is undefined.