Describe IPv6 format in docstring for 'make-network-process'

* src/process.c (Fmake_network_process): Add description of IPv6
address format.
1 job for master in 66 minutes and 17 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
failed #4141
test-all

01:06:17

 
Name Stage Failure
failed
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
make: *** [check-expensive] Error 2
Makefile:959: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1