MAINT: spatial: static, unused code, sqrt(sqeuclidean)
MAINT: spatial: static, unused code, sqrt(sqeuclidean)

Made the functions in distance_wrap.c static. No need to pollute the global
linker namespace with these; they're passed to Python using a table of
function pointers.

datamade/hcluster,datamade/hcluster,datamade/hcluster