[PCF7931] draft continue with refactoring ReadPCF7931()

still not done with DemodPCF7931(). But now including changes in  ReadPCF7931().
They work tightly together.
Trying to resolve some issues and bugs. Basically it seems to work and
my results are consistent. However, they still deviate from what I get if
I do analyze the signal using lf read and data commands.

still some issues somewhere.

armsrc/pcf7931.h

@@ -20,7 +20,6 @@
 
 
 typedef enum{
-    UNDEFINED,
     FALLING,
     RISING 
 } EdgeType;