Neither decreasing the src winheight or increasing the cmd winheight causes the 
observed cmd winheight to increase.

1) Fire up gdbtui v7.1
2) winheight src -10
3) p (repeatedly)

Observe the window borders change but the scrolling cmd window stays in the same 
fixed region of the window.

1) Fire up gdbtui
2) winheight cmd +10
3) p (repeatedly)

Ditto.  Refreshing with 'refresh' helps neither case.

I expect that either action will cause the scrolling cmd region to increase in 
side.