When I try to compile certain programs, I get the following link error:
	Undefined:
	_XShapeQueryExtension
	_XShapeCombineMask

	These routines are actually part of the Shape Extension to X (SHAPE)
which was introduced in the X11R4 distribution and allows non-rectangular
windows.  Like the other sample server extensions, the shape extension will 
only run on a server which supports it.  Pre-X11R4 servers, as well as many 
vendor-supplied servers, do not support the shape extension, in which case 
they will display rectangular windows anyway.

	In order to use the shape extension, you must link to the library 
libXext.a.  In the X11 distribution, this library and the associated includes
will be in the mit/extensions directory.  If you do not have these files, do 
not despair:  many freeware programs which use the shape extension can also be 
compiled without it by removing the -DSHAPE define from the Makefile; you can
probably do this and compile successfully against your older vendor-supplied X 
libraries.

[from John B. Melby, melby%yk.fujitsu.co.jp@uunet.uu.net, 3/91]