binds...
* ctrl + shift + m1 (in texbro): open shader in external editor
misc...
* fix: do not unmaximize external shader editor on win
* fix: blank cursor in radiant after calling external shader editor on win
* fix shader editors stuff for non uindowses
* 'Shader Editor Command' preference is available on win (is used, if set; otherwise try default os action for file)
* fix: 'Shader Editor Command' preference allows selecting executable via dialog
* GDK_HAND2 cursor in clipper tool mode
* fix: clipper points have numeric labels
* '2d zoom in to mouse pointer' option works for alt + m2 zoom
* '3d zoom in to mouse pointer' option (def = yes)
