PSD article7:  implementation and tests of Vector2 class in C

Files:

vector2.h:	class definition (no methods) of Vector2 class in C

vector2.c:	class implentation of Vector2 class in C

testsupport.h:	unit testing support - prototypes and macros

testsupport.c:	unit testing support - functions

simpletestvector2.c: simple tests for vectors, print the answers

testvector2.c:	unit tests for vectors, answers encoded, only complains about failures
