merge r1604590 from trunk:

correct doc for apr_skiplist_pop -- "leaving the element in the skip list."
text inadvertently copied from apr_skiplist_peek().

Submitted By: Takashi Sato <takashi tks st>
Committed By: covener


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/branches/1.5.x@1604593 13f79535-47bb-0310-9956-ffa450edef68