[whatwg] return lowercase hex values for fillStyle and strokeStyle

[Christoph Päper]

*Anne van Kesteren*:
> Instead of returning an uppercase six digit hex value I suggest  
> returning a lowercase value for compatibility with what UAs  
> (including IE) currently do

It may be the right decision on compatibility grounds, but other than  
that lowercase hexadecimal digits (0-9, a-f) are almost always a bad  
choice, because a, c and e have no ascenders like every hindu-arabic  
decimal digit has and thus make the number harder to read. This  
obviously does not apply to fonts with old-style numerals aka. text  
figures, where 0, 1 and 2 have neither ascenders (like 6 and 8) nor  
descenders (like 3, 4, 5, 7 and 9), but those are rather unlikely to  
be used in a programming environment.