Merge r1799435, r1799437, r1805206, r1805322 from trunk:

Allow WatchdogInterval to be sub 1 second

Allow finer control over hcheck intervals... minimum is whatever
the watchdog slice is.

Fix remaining lint from ms capability for hchecks.

userland change = we now are OK w/ ms


Submitted by: jim
Reviewed by: jim, covener, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1807772 13f79535-47bb-0310-9956-ffa450edef68