add ability to have a file, ~/.asterisk.makeopts, that will be included in

the makefile so that every time you checkout Asterisk, you don't have to
edit the makefile to set all of your common options


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6127 65c4cc65-6c06-0410-ace0-fbb531ad65f3