mod_remoteip: Add PROXY protocol support

trunk patch: http://svn.apache.org/r1776575
             http://svn.apache.org/r1776578 (doc fix)
             http://svn.apache.org/r1776624
             http://svn.apache.org/r1776627 (shortened name + doc fix)
             http://svn.apache.org/r1776674 (attribution moved to CHANGES)
             http://svn.apache.org/r1776734
             http://svn.apache.org/r1776740 (attribution updated in mod_remotip.c)
             http://svn.apache.org/r1778268 (fix compiler warning)
             http://svn.apache.org/r1780725 (set buckets aside)
             http://svn.apache.org/r1781030 (fix strict GCC warning)
             http://svn.apache.org/r1781031 (reference the filter by handle)
             http://svn.apache.org/r1781701 (rework optional processing case)
             http://svn.apache.org/r1788674 (final edge cases/ignore slave conns)
             http://svn.apache.org/r1789800 (remove optional processing)
             http://svn.apache.org/r1790169 (rename "exception" directive)
             http://svn.apache.org/r1790457 (Update directive name in err message)
             http://svn.apache.org/r1790691
             http://svn.apache.org/r1806985
             http://svn.apache.org/r1818279
2.4 convenience patch (includes CHANGES):
             http://home.apache.org/~ylavic/patches/RemoteIPProxyProtocol.2.4-v3.patch
+1: druggeri, jim, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1824221 13f79535-47bb-0310-9956-ffa450edef68