pcntl add darwin specific flags for who/which especially (#7075)

PRIO_DARWIN_BG to be on part with pthread QOS class and
 energy efficiency.

Author: devnexen

ext/pcntl/pcntl.c

@@ -167,6 +167,10 @@ void php_register_signal_constants(INIT_FUNC_ARGS)
 	REGISTER_LONG_CONSTANT("PRIO_PGRP", PRIO_PGRP, CONST_CS | CONST_PERSISTENT);
 	REGISTER_LONG_CONSTANT("PRIO_USER", PRIO_USER, CONST_CS | CONST_PERSISTENT);
 	REGISTER_LONG_CONSTANT("PRIO_PROCESS", PRIO_PROCESS, CONST_CS | CONST_PERSISTENT);
+#if defined(PRIO_DARWIN_BG)
+	REGISTER_LONG_CONSTANT("PRIO_DARWIN_BG", PRIO_DARWIN_BG, CONST_CS | CONST_PERSISTENT);
+	REGISTER_LONG_CONSTANT("PRIO_DARWIN_THREAD", PRIO_DARWIN_THREAD, CONST_CS | CONST_PERSISTENT);
+#endif
 #endif
 
 	/* {{{ "how" argument for sigprocmask */