sympy/sympy — pull request #1271 by jrioux (2012-04-30 09:42:00+00:00)
Title: Fix derivatives of complex functions w.r.t. complex variables

Fixes the wrong result from http://code.google.com/p/sympy/issues/detail?id=2662
Also implement sign(x).doit() to address http://code.google.com/p/sympy/issues/detail?id=2664