Added more Remez code, and appoximations for erf/erfc inverses.
Updated and refactored erf code to use new approximations.
Added more test cases.
[SVN r3210]
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]