render effect segv, drag chkbox track coords, check mask active,

render effect segv, drag chkbox track coords, check mask active,
crop vattachment vfrm copy, gl flip_y coords twice,
mask segv if no tracks armed,
always ins clip at pos 0 in load append new trks,
change load mode text to Paste over selection,
add gl_probe for shader lang version 4.3,
titler updates gui if ovly coords change,