WIP integrate cpcrslib.
More pretty messages. 'make clean' rule.
Ignore *.buildtree *.installtree directories not files.
More pretty messages.
Cleanup: replace use of dirname with GNU Make automatic variables.
Use MAKE makefile variable to propagate command-line argument to sub-invocations of make.

Useful for "make -j8".
Basic support for cpcrslib. Would be better if it compiles examples.