Add Random unit tests

Add Random unit tests.

This adds a variety of unit tests for randomness. Most are straightforward. The gorilla test is for checking how random the individual bit places are. The suite only tests SkMWCRandom because SkRandom fails a number of them, in particular the uniform byte test, the gorilla test and the range test. Suggestions for more tests are welcome.

[Humper, 2013-02-08 15:03:52]

This looks great to me (lGtm?).  Important stuff, thanks.

[bsalomon, 2013-02-08 15:04:20]

On 2013/02/08 15:03:52, Humper wrote:
> This looks great to me (lGtm?).  Important stuff, thanks.

lgtm, too.

[JimVV, 2013-02-08 16:38:29]

On 2013/02/08 15:04:20, bsalomon wrote:
> On 2013/02/08 15:03:52, Humper wrote:
> > This looks great to me (lGtm?).  Important stuff, thanks.
> 
> lgtm, too.

Sorry, a couple of small updates. I changed the normal distribution CDF out for
a cheaper one and added an assert to ensure that our nextRangeU values are
actually in range.

[bsalomon, 2013-02-08 17:09:11]

On 2013/02/08 16:38:29, JimVV wrote:
> On 2013/02/08 15:04:20, bsalomon wrote:
> > On 2013/02/08 15:03:52, Humper wrote:
> > > This looks great to me (lGtm?).  Important stuff, thanks.
> > 
> > lgtm, too.
> 
> Sorry, a couple of small updates. I changed the normal distribution CDF out
for
> a cheaper one and added an assert to ensure that our nextRangeU values are
> actually in range.

lgtm

[JimVV, 2013-02-08 17:13:58]

On 2013/02/08 17:09:11, bsalomon wrote:
> On 2013/02/08 16:38:29, JimVV wrote:
> > On 2013/02/08 15:04:20, bsalomon wrote:
> > > On 2013/02/08 15:03:52, Humper wrote:
> > > > This looks great to me (lGtm?).  Important stuff, thanks.
> > > 
> > > lgtm, too.
> > 
> > Sorry, a couple of small updates. I changed the normal distribution CDF out
> for
> > a cheaper one and added an assert to ensure that our nextRangeU values are
> > actually in range.
> 
> lgtm

Committed as r7670.