XSB Src (SVN)-old

Fixed read_canonical and write_canonical to handle a() forms.

Note: read_canonical will *not* recognize a( ), i.e. with a whitespace
between the parens. Since this is read_canonical (and write_canonical
produces the accepted form,) I think this is OK. It's a more
complicated fix if we were to accept the form with the whitespace.

Fixed atom(a()) to fail, and compound(a()) to succeed.
(Had been intentionally programmed to be the opposite, for some reason.
System self-compiles and all tests pass with this change. It is now
consistent with SWI's implementation of the f() form.)

cleanup in dbdrivers package

Minimal documentation for table_index directive. (There may be a better
place in the manual for this? And it needs to be expanded if it stays.)

Minor fix to concat_atom to handle integers more consistently.

Added code to support table_index directive (abolish_table_index_pred)

New table_index directive to use subsumptive tables to do more general
indexing of tables.

Previous adding of cast in tab_structs.h broke. Interestingly the
smaller (level_num) needed to be cast to the larger (flags{..]) since
the flag really held a number greater than 32 bits.)

Added CYGWIN test to allow definition of PTHREAD_MUTEX_ERRORCHECK_NP
and friends so cygwin compilation could get further. Teri has a
comment just before this change (line 217 in thread_xsb.h) which
sounds relevant, but I don't understand it. Is this what was meant?
Or was it to say that this change of mine is probably wrong?

Explicit casts to quiet persnickety compiler.

Added some casts (and some slightly different type decls) to quiet
warnings in MSVC on Windows 10.