now providing new position of child relative to parent in the position

now providing new position of child relative to parent in the position
callback
also need to set position func for the child window in the resizer demo

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1480 7f0cb862-5218-0410-a997-914c9d46530a