Merge pull request #853 from hintjens/master

Minor maintenance
Dir patch does not duplicate delete patches

Problem: The zdir_patch object does not duplicate a patch that is
a delete operation. The duplication method requires that the file's
digest is not NULL, but a delete operation will not have a file to
read to calculate the digest.

Solution: Added a test for the operation type before the zdir_patch
object is destroyed for having an empty digest.
Merge pull request #854 from danriegsecker/master

Dir patch does not duplicate delete patches
Ref #855
Merge pull request #857 from keent/master

Ref #855
Problem: should be possible to clear cached file digest on file instances

Solution: call zdigest_destroy on zfile_restat
and inline zfile_close in zfile_digest

Other solutions are possible:
* provide explicit method to clear the file digest
* don't cache the digest
Merge pull request #858 from skaes/zfile_restat_should_reset_file_digest

Problem: should be possible to clear cached file digest on file instances
Problem: make debug does not work on OS X

Solution: call proper libtool
Merge pull request #859 from skaes/master

Problem: make debug does not work on OS X
Added va_list versions zsock_vsend/vrecv of zsock_send/recv; calling these from zsock_send/recv
Merge pull request #860 from lovmoen/master

Problem: There are no va_list versions of zsock_send/recv picture messages.
Problem: No succint way to compare two zmsgs
Solution: Add zmsg_eq (similar to zframe_eq)
Merge pull request #861 from jemc/master

Problem: No succint way to compare two zmsgs
Problem: zstr_recvx did not conform to documentation

Solution: return number of strings stored, rather than always
returning 0.
Problem: selftest runs out of ephemeral sockets on TravisCI

Solution: increase ephemeral range from 10 to 50 sockets, in test
case.
Problem: multi-line if statements were misformatted

This stems from an experiment in autoformatting the source code.

Solution: whitespace fixes to revert if statements to prior state.
Problem: search/replace went wrong

Some bogus edits caused syntax errors. Solution: fix these.
Problem: need way to create/check/decode signal messages

This is to allow signals to be sent and mixed with other messages
on sockets, instead of just depending on zsock_signal/_wait.