[Cfp-interest] functions - document updated

[Jim Thomas]

I placed an updated Functions.pdf on the CFP wiki under 
Topics/Functions/Attachments. The date on it is 11 Aug 2010. Please note 
the following changes:

	Added some introductory text
	Cleaned up example in 4
	Integrated David's text for 5, updated rationale
	Listed cr prefixed names to be reserved in 11
	Noted functions to go in <fenv.h> instead of <math.h>
	Integrated David's implementation note in 13

-Jim