an alternate faster definition of pow(x, y)

	06/26/2013 (dlm)	powe(): an alternate definition of pow(x, y) for
x>0... this is faster (ca. 20%) then the one in math.h, but comes with
a cost as the precision is slightly lower.  The measured precision drop
I was getting was at max a relative error of about 100 billion percent
(12 places after the decimal point) per calculation though so I don't
think it's a big deal... (though it's hard to even accurately tell)
						--> replaced pow() throughout the code with powe()