bug#16738: Errors while resizing vertically

[martin rudalics]

>> 2 canonical lines.  But this is to be expected?  Otherwise, Emacs would
>> truncate the text line by the extra pixels needed for the mode line.
>
> The finer details of pixel and character coexistence on graphical frames tend 
escape me. If I encounter any more errors, I will report them.

Suppose you have a canonical character height of 8 pixels and a header
and a mode line with 2 additional pixels each.  If you now set
`window-min-height' to 1, Emacs will display a text line of 4 pixels
height if we do not round appropriately.  That wouldn't look good.

martin