Need to pass vel=true arg to create_interpolated_tree*.
Hack: pass velocity back to specks in SEPVAL argument for leaf nodes.

Allow multiple requests per connection -- leave connection open
until we get EOF.

Accept T=<scalefactor> as well as T=<16 numbers>.
Report density center both in original and transformed coords.

isalpha for Irix 6.5 back-compat.

Return more complete information -- transform etc. -- when
asked for neither speck nor sdb data.