Send ALARM_CLOCK_CHANGED broadcast with REPLACE_PENDING

Spammy behavior, including app bugs, has been seen in the field to induce
situations where there were thousands of duplicate ALARM_CLOCK_CHANGED
broadcasts in the queue awaiting delivery.  They're relatively inexpensive
to deliver but not free, and this has considerable impact on both the
system's ability to issue broadcasts and the ability of this broadcast's
subscribed receivers to do other work besides processing them.

Bug 26910849

Change-Id: Ic91f25514a26d41a1b1b4cb44489d1575fe1867c