Fix bug where option-click with scrollback overflow moved a crazy number of lines vertically. Don't accept option-click's outside the live area. Fixes issue 3347.

Change selection highlight style to use default; NSTableViewSelectionHighlightStyleSourceList uses vibrancy.

Conflicts:
	Popup.m

Conflicts:
	Popup.m

Bring over environment setting code from master branch to avoid duplicate env vars in 10.10 (possibly an OS bug, but better safe than sorry).

Reduce max length for custom actions to 400 bytes because some regexes are very slow. See issue 3056