[!MAC_OSX] Don't include keyboard.h.

[!MAC_OSX] Don't include keyboard.h.
[!MAC_OSX] (select): Try detect_input_pending before ReceiveNextEvent
in the same BLOCK_INPUT block, in case that some input has already
been read asynchronously.  Pretend to be interrupted by a signal
if some input is available.
[MAC_OSX] (select_and_poll_event, sys_select): Likewise.
(SELECT_POLLING_PERIOD_USEC) [SELECT_USE_CFSOCKET]: Change to 100000.
Now used for ReceiveNextEvent timeout instead of select timeout.
(EVENT_CLASS_SOCK) [SELECT_USE_CFSOCKET]: Remove macro.
[SELECT_USE_CFSOCKET] (socket_callback): Add non-blocking connect
support.  Quit event loop.
[MAC_OSX] (sys_select) [SELECT_USE_CFSOCKET]: Add non-blocking
connect support.  Reuse previously allocated CFRunLoopSource.
(Fmac_process_hi_command) [TARGET_API_MAC_CARBON]: New function.
(syms_of_mac) [TARGET_API_MAC_CARBON]: Defsubr it.