julia 0.5 compatibility + new derivatives definitions

• restores compatibility with latest julia 0.5
• add derivatives definitions for :
  • tan, sinh, cosh, tanh,
  • asin, acos, atan,
  • round, ceil, floor, trunc, mod2pi,
  • log1p, expm1,
  • erf, erfc, gamma, lgamma, beta and lbeta