API changes to event handling

[zephyrbot]

Reported by Benjamin Walsh:

A potpourri of potential enhancements:

• Allow object to pend signals in a cumulative way using the semaphore in a non-binary way.
  

(Imported from Jira ZEP-928)

[zephyrbot]

by Sharron LIU:

I recalled there's another story on zpoll, for similar purpose?

[zephyrbot]

by Benjamin Walsh:

No, this is different: it's for the kernel event object, which is different than k_poll.

[zephyrbot]

by Mark Linkmeyer:

Per email from Ben Walsh on 10/18/16, this story is on track for 1.6.

[zephyrbot]

by Benjamin Walsh:

Fixed by 058fa4e

[zephyrbot]

by Sharron LIU:

alert verified @x86 @arc @arm with below test points:
/*TESTPOINT: init via K_ALERT_DEFINE/
/*TESTPOINT: init via k_alert_init/
/*TESTPOINT: thread-thread sync via alert/
/*TESTPOINT: thread-isr sync via alert/
/*TESTPOINT: alert send/
/*TESTPOINT: alert send when meeting pending limit/
/*TESTPOINT: alert recv/
/*TESTPOINT: alert recv -EAGAIN/
/*TESTPOINT: alert recv -EBUSY/
/*TESTPOINT: alert handler default/
/*TESTPOINT: alert handler ignore/
/*TESTPOINT: alert handler return 0/
/*TESTPOINT: alert handler return non-0/

Closing this. Thanks.

minor issue observed in "kernel primer v2" doc, logged as GH-2725