apr port not selecting the right shared memory scheme

Hello, The Apache Portable Runtime Library selects shmget to get shared memory, but it doesn't work well on OSX http://developer.apple.com/ technotes/tn2002/tn2071.html MMAP_SHM doesn't work well either, and I found out MMAP_TMP was working, so that I propose the following change to the apr port file. fred