Some unit tests

Attached is a gzipped tar file with a "tests" subdirectory for libwww, 
and a start on unit tests using the C "check" unit testing framework. I 
downloaded the latest release (check-0.9.2) from sourceforge yesterday. 
The one test suite in there now exercises most of the operations in 
"HTList" which is a foundational thing for a lot of the other core and 
utility methods. And it passes :-)

The Makefile is hardwired for my configuration - sorry about that, I'm 
no expert at automake etc.

          Arthur