Fix Jirs 255
The DAP code compiles constraints into an internal
tree form. When it goes to fetch data, it converts
that tree form into a string suitable for use in a url.
The tree->string code was using '<' when it should be
using '<=' and vice versa.
The fix is to make sure the right operator is used.


git-svn-id: https://sub.unidata.ucar.edu/netcdf/trunk@3238 2e3060e4-1ed8-cf1f-9cc2-9586e844a556