Lots of changes here. Added new I2C test code, a new serialTest program,

and developed the new ISR - Interrupt Service Routine
handler - much easier than the old waitForInterrupt code!

Minor tweaks to the gpio program to recognise the environment variable
WIRINGPI_DEBUG too, and removed the printing of the errors from the
main wiringPi setup routines (and added some new ones!)

examples/okLed.c

@@ -17,6 +17,7 @@
 #include <string.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <math.h>
 
 #include <wiringPi.h>
 #include <softPwm.h>