* Rewrite of error queue code: errors are now pulled, instead of being turned into messageboxes automatically.

Use built in sort indicator of ListView control (on windows), wx doesn't provide this, so we do some Win32 programming.

This requires that we ev.Skip() EVT_MOTION, otherwise the list becomes very sluggish to update.

Angles are always doubles.
Internally use radians as much as possible.

 * sin, cos, tan (radians)
 * sin_deg, cos_deg, tan_deg (degrees)
 * exp, log (base e), log10
 * sqrt, pow

fixed vector subscript out of range error in the Graph control: stacked bar charts ::findItem used incorrect bound