Obsolete erc-send-pre-hook and add new erc-pre-send-function

* lisp/erc/erc.el (erc-send-pre-hook): Make obsolete.
(erc-send-input): Ditto.
(erc-pre-send-function): New function.
(erc-send-input): Use the new function, and silence byte
compilation warning about the dynamic variable `str' used by the
now-obsolete hook.
1 job for master in 66 minutes and 55 seconds (queued for 2 seconds)
Status Job ID Name Coverage
failed #2169


Name Stage Failure
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: 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:957: recipe for target 'check-expensive' failed
ERROR: Job failed: exit code 1