added NaN test for bessel_first_kind
added NaN tests for agrad/bessel_first_kind
added NaN and derivative doc for bessel_first_kind in manual
switched to no namespace version of cbrt
added NaN tests for cbrt
added NaN and derivative doc for cbrt to manual
added NaN test for ceil
add failing NaN test for ceil
fixed NaN gradient for ceil using unlikely()
added NaN test for ceil
switched to no namespace version of ceil
added NaN and derivative doc to manual for ceil
switched to no namespace version of cos and sin
added NaN tests for cos
added NaN and derivative doc to manual
switched to no namespace version of cosh and sinh
added NaN tests
added NaN and derivative doc for cosh in manual
switched to no namespace version of exp
added NaN test for exp