- solidify/Makefile: added solid.o
- solidify/solid.h, solidify.c (height_field, povray): output the part as
the intersection of two height fields
- solidify/solidify.c (main): generate POV-Ray output if stdout is
redirected
- solidify/Makefile (run, pov, disp): targets to run a test setup, render
it, and display the result
- solidify/main.pov: simple scene showing the test part
