Stop alt-spacebar window menu

[Bill Farmer <williamjfarmer tiscali co uk>]

I am porting a native windows application to linux gtk. I want to stop 
the alt-spacebar key combination popping up the application window menu. 
This can be done in windows by capturing the WM_SYSCHAR message. After 
searching though the gtk documentation and sources, the only way I can 
see to do this is by copying a file from the gdk sources, modifying it, 
and compiling it with the application. This is complicated by the latest 
gtk source tarball not including gdk. Is this because gdk hasn't changed 
since the last version that contained it? Am I missing something?

Regards
Bill