#685 fonts overlapped when scrolling

[Jijuan Zheng]

when the top-left corner of nedit window is not at (0,0) position of the desktop display (i.e., not sit at the top left corner), any scrolling of the window text, no matter use mouse or keyboard, fonts will overlap to each others and hard to read. I had seen a solution proposed in another ticket using
XLIB_SKIP_ARGB_VISUALS=1 but this doesn't help. (https://sourceforge.net/p/nedit/bugs/517/)
This will be fixed as long as I move the nedit to the up-left most position (0,0), then no matter how to scroll nedit windows, all display are neat.

Also, symptom is worse when scrolling up compared to scrolling down. screen shots attached.

I had tried nedit 5.3, 5.4 5.5 32 bits (downloaded binary) and also compiled 5.7 64 bits , all same result. It only happened in Suse leap 42.3, it doesn't happen to Suse Leap 15 or 15.1, but I cannot use Suse 15.x because they have two bugs prevents me using it.