Fix gcc errors

git-svn-id: https://gpac.svn.sourceforge.net/svnroot/gpac/trunk/gpac@4450 63c20433-aa62-49bd-875c-5a186b69a8fb
Fixed bugs with SDL and latest ffmpeg, added sdl2-config support

git-svn-id: https://gpac.svn.sourceforge.net/svnroot/gpac/trunk/gpac@4451 63c20433-aa62-49bd-875c-5a186b69a8fb
Fixed resize with SDL2

git-svn-id: https://gpac.svn.sourceforge.net/svnroot/gpac/trunk/gpac@4452 63c20433-aa62-49bd-875c-5a186b69a8fb
Fixed init bug with variable rate live TS

git-svn-id: https://gpac.svn.sourceforge.net/svnroot/gpac/trunk/gpac@4453 63c20433-aa62-49bd-875c-5a186b69a8fb
GF_TRUE/GF_FALSE