Fixed a bug in ap_rgetline()

Fixed a bug in ap_rgetline()
When an input line required more than one read, each subsequent
block of data was copied on top of the previous one.  So if a
request line got split into multiple packets, the data would be
corrupted.  The new code uses a power-of-two allocator to expand
the buffer and properly append the next block of data at the end
of the previous one.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@92558 13f79535-47bb-0310-9956-ffa450edef68