[vtkusers] autoconf macros to check for VTK

[tom fogal]

Anybody out there writing software that uses VTK and builds with
autoconf? In my current projects that need it I'm forcing users to
specify --with-vtk=/path/to/vtk as an argument to the ./configure
script, but this is less than ideal.

Anyone else run into this before? Do you have your own custom autoconf
macros to look for VTK in some obvious paths? Would you like to share?
=)

-tom