XSB Src (SVN)-old

Changed defn of ?=/2 to avoid laying down a choicepoint.

A number of documentation changes, mostly suggested by Ulrich Neumerkel,
having mostly to do with ISO issues.

Changed format spec to agree with variable type.

Moved xsb_sprint_variable, since for some reason DllExport didn't
seem to work for it on MSVC32 compiler over in builtin.c.

xwam update

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).