Renamed sqrtp1m1 as sqrt1pm1 to match log1p etc.
Added docs for misc power functions, plus weibull distribution.
Updated tests to match the above changes.
[SVN r3321]
Added code for extracting the sign of a number.
Fixed a few bugs and tidied up the code a little in places.
Changed test_result to properly encapsulate it's contents.
[SVN r3106]