ENH: special: add inverse Box-Cox transform
GEN: special: run generate_ufuncs
MAINT: stats: use inv_boxcox in genpareto
Merge pull request #4211 from ev-br/inv_bcx

add an ufunc for the inverse Box-Cox transfrom
Merge pull request #4215 from manns/master

DOC: splprep documentation updated to reflect dimensional limitation