[vtkusers] Compile Abstract Class for Tcl

[John Biddiscombe]

> I have tried it both with the file extention and with out. Either way the
> TCL parser tries to create a NewCommand for the class and then the
> compiler gives and error because my abstract class does not have a New

Delete the myAbstractClassTCL.cxx file!

When you run the makefile it sees that the myxxx.h file is newer than the
tcl wrapper and regenerates the wrapper. If you then alter the cmakelists
file and make it abstract, the tcl wrapper isn't smart enough (or looking in
the right place really) to realize it changed from concrete to abstract.
Delete the tcl.cxx file and then it'll regenerate it without the new command

JB