Implemented tip-427: socket fconfigure option -connecting plus no -peername,-sockname when still connecting.
Merge trunk
New tests: 14.16: -peername empty while async connect running, 14.17: -sockname
fconfigure -peername and -sockname return empty string while async connect running.
[10dc6daa37] [gets] on a non-blocking channel must take care so that
    1) At least one call to the channel driver input proc gets made.
       Failure to do this locks up the channel - catastrophic FAIL. 
    2) After any driver call reports BLOCKED, don't call again.
       This is less serious, but FAILs to respect the non-blocking setting.
Code corrections and tests included, to restore 8.5.15 compat.
[10dc6daa37] New fix for [gets] on non-blocking channel.  This time
properly accounts for the effects of ENCODING_LINESIZE.
[10dc6daa37] New fix for [gets] on non-blocking channel. This time properly accounts for the effects of ENCODING_LINESIZE.
merge trunk