[lazarus] broken gtk+ compatibility

[Giuliano Colla]

With rev. 11861 I started having problems with some versions of gtk+ 
libraries.
Transparent parts of glyphs are shown in black. This happens with FC1 
(gtk+1.2.10-28.1) but not with FC5 (gtk+1.2.10-50). As this problem 
didn't exist before, I presume that some change has been made which has 
broken the compatibility.
I enclose two screenshots of the same application running under FC1, one 
compiled with revision 11860, the second with revision 11862 (11861 
didn't compile). One can easily see the black areas in the speed button 
glyphs and in the dialog question mark.
I tried to figure the problem, but rev. 11861 introduced quite a lot of 
changes and I got lost.

Thanks
Giuliano
<<inline: i11860.png>><<inline: i11862.png>>