mod_lua: Sync 2.4 branch with trunk. This includes (but is not limited to)

      Server pools, new apr functions for the request_rec table, input/output filters,
LuaCodeCache, LuaMapHandler and multipart form data handling. This is long
overdue, and has become too spaghetti-ish to propose in chunks :|

trunk patch: http://svn.apache.org/r1366890
             http://svn.apache.org/r1367025
             http://svn.apache.org/r1367040
             http://svn.apache.org/r1367048
             http://svn.apache.org/r1383024
             http://svn.apache.org/r1383028
             http://svn.apache.org/r1383037
             http://svn.apache.org/r1367725
             http://svn.apache.org/r1367875
             http://svn.apache.org/r1368109
             http://svn.apache.org/r1369656
             http://svn.apache.org/r1369793
             http://svn.apache.org/r1369800
             http://svn.apache.org/r1370158
             http://svn.apache.org/r1433967
             http://svn.apache.org/r1429169