First attempt at an implementation of a non-blocking shared port client.
Fix handling of NULL char *; fix non-blocking logic. #4094
Mark socket as non-blocking when a connection attempt is made. #4094

This causes clients to be rejected as soon as the daemon's backlog
is hit.  This is equivalent behavior to the case where the daemon
is listening on the network and the TCP socket backlogs.
ifdef out portions which will not compile under Windows. #4094
Merge branch 'master' into shared_port_nonblocking
Merge branch 'master' into shared_port_nonblocking
Merge branch 'master' into shared_port_nonblocking
Merge remote-tracking branch 'github/shared_port_nonblocking' into shared_port_nonblocking
Attempt to make the shared port transparently forward collector connections.
Allow shared port to peacefully coexist with the collector. #0
Have COLLECTOR_USES_SHARED_PORT do the requisite configuration. #3813
Gittrac #4171:  Split a bunch of lines with continuation characters
to make sure that works properly.
Gittrac #4171:  Fixed the basic problem, but lots of cleanup needed
(including other places that use the "read a whole file into a string"
functionality).
Gittrac #3843:  We no longer look at HTCondor submit files if we're in
default/workflow log mode; also, we no longer distinguish between
using the default log for a node because we're in workflow log mode
overall vs. using the default log because there's no log file specified
in the submit file -- that simplifies a bunch of the code.
Gittrac #4171:  Cleaned up and documented the MultiLogFiles::FileReader
class.
Changed things around so that we only generate the event mask
string once, since it's the same every time.
Gittrac #4171:  Should be pretty much finished up -- DAGMan no longer
uses any of the "read a whole file into a string" methods, except for
finding the log file for a Stork submit file; removed a bunch of
MultiLogFile methods that used or implemented the "read a whole file
into a string" functionality.  (Still needs version history entry.)
Gittrac #4171/gittrac #3843:  Added version history items for these
bug fixes.
Merge branch 'V8_0-gittrac_4171-branch' into V8_1-gittrac_4189-branch
Gittrac #4189:  Initial merge is complete, but needs further checking
and maybe extension of the DAGMAN_USE_OLD_DAG_READER configuration
macro.  Also, the job_dagman_dont_use_default_node_log test fails for
a reason I haven't figured out yet.
Gittrac #4189:  Fixed manual merge error that caused
job_dagman_dont_use_default_node_log to fail.