Merge pull request #10 from edisonm/master

FIXED: Bug in subterm_pos that was causing cyclic terms
FIXED: Colour tokens for module-qualified predicate indicators.
FIXED: library(prolog_colour): Several issues: qualified terms,
empty lists, failure on illegal meta-predicate specifications,
control operators of DCG bodies.
Updated http
Updated documentation
ADDED: PL_get_stream(), replacing PL_get_stream_handle() and adding a
flags argument.
Document that Sclose deals safely with an erased stream.
MODIFIED: do not complain if close/1 is called on a stream pair of
which one or both streams are already closed.
DOC: Issues around close/1 and stream pairs.
MODIFIED: Allow stream_pair(+,-,-) with a stream argument and do not bind already closed streams
Updated http
Added websocket.dll to the Windows installer
Updated http
Updated semweb
Updated ssl
Updated http
Updated http
Updated pengines
FIXED: library(prolog_colour): avoid error if option value is a function.
Updated http