XSB Src (SVN)-old

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.

Changed way to find current windows system in order to get tome. (Old
way deprectaed and this is suggested new way.)

Fixes to hopefully get XSB to compile on Windows with message queues.
I commented out the mq locks for the sequential Windows version.

Also, some code to enable MQs to be called from C.

Ifdeffed the use of mutex attributes for Windows.

Implemented interrupts with goals for sequential engine -- an analog
of thread signal queues. Curr_sym.* is other setup for tripwires, which wont interfere with anything.

Implemented version of message queues for single-threaded engine, to
support interrupts with general goals.