document why the makefile uses an unusual include path
document why the makefile uses an unusual include path

git-svn-id: f26ccc5efe72c2bd8e1c40f599fe313f2692e4de@7129 a612230a-c5fa-0310-af8b-88eea846685b

sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror,sipXtapi/sipXtapi-svn-mirror