MAINT: stats: Use explicit formulas for the mean, variance, skew and kurtosis of the loggamma distribution.
TST: stats: Add a test for the loggamma distribution stats.
STY: stats: fix line length
BUG: stats: Fixed the calculation in pareto.stats() to avoid RuntimeWarnings

In pareto.stats(), in the calculation of the skewness, a variable 'bt' is
defined as 'bt = extract(b > 3, b)', but 'b' was still used in the
calculation.  This would lead to spurious RuntimeWarnings.
MAINT: stats: micro-optimization in loggamma stats method--reuse the value of var
Merge pull request #2548 from WarrenWeckesser/stats-loggamma

MAINT: stats: Use explicit formulas for the loggamma stats.
Merge pull request #2550 from WarrenWeckesser/bug-stats-pareto-skewness

BUG: stats: Fixed the calculation in pareto.stats() to avoid RuntimeWarnings