added NaN test for inv_logit
added NaN test for inv_logit

stan-dev/math,stan-dev/stan,stan-dev/stan,stan-dev/math,stan-dev/stan,stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/stan,stan-dev/math,stan-dev/math,stan-dev/math