distcache already demonstrates sub-second resolutions, but much more

importantly, let us not introduce more Y2k38 bugs?

Changes the ->store method to take expiry as an apr_time_t, and introduce
a placeholder to implement provider-specific iterators of the current
elements of an socache store.

Cleans up confusion where expiry might be confused with a timeout-period.

Finally clean up some hUngarian noteAtion.  Someones' hands need to be slapped.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@907917 13f79535-47bb-0310-9956-ffa450edef68