bug#36633: Scrolling by pixels: visible stretch glyphs overwrite header-line.

[Keith David Bershatsky]

I applied the following patch:

0001-Fix-stretch-glyphs-overlap-with-line-above-bug-36633.patch

and can confirm that the header-line is no longer being overwritten by the 
visible stretch glyphs as described in the initial post as to issue 36633.  
Thank you for your work on this issue!

The following is a screenshot of the results with the above-mentioned patch 
applied:

https://youtu.be/g8DkCW-vaKA