#4967 cdf_lognormal and pdf_lognormal error at x = 0

[David Scherfgen]

cdf_lognormal(0,0,1) raises "log: encountered log(0)" instead of returning 0

Maxima 5.49post, SBCL 2.6.7.

(%i1) display2d:false$
(%i2) load(distrib)$
(%i3) print(errcatch(cdf_lognormal(0,0,1)))$
log: encountered log(0).
[]
(%i4) cdf_normal(0,0,1);
(%o4) 1/2

Expected: (%o3) = 0. The lognormal distribution has support (0,inf) with cdf(0) = 0 and pdf(0) = 0 as limits; every other cdf_* in the package returns a value at the edge of its support.