More refactoring to completely (?) mimic previous library behavior for scanning contents of the file

Switch test for nc_inq_unlimdim and nc_inq_unlimdims to use the same ordering as the rest of the dimension queries.  Correct error in library where types used in sub-group variables but that were added to the file after the sub-group was created weren't available for sub-group variables to use.  Start cleaning up test suite and un-commenting tests that were commented out (got up to nc_test4/tst_fills2.c, alphabetically) before running into an error in HDF5.