"SHOW GRID" incorrectly lists axes as compressed

[AnsleyManke]

This begins with Ferret v7.5. Versions prior to that were correct. A user reports to the Ferret list,

use coads_climatology
let sst_demean =  sst - sst[x=@ave,y=@ave]
show grid sst_demean
    GRID GSQ1
 name       axis              # pts   start                end                 subset
 COADSX    LONGITUDE          180mr   21E                  19E(379)            compressed
 COADSY    LATITUDE            90 r   89S                  89N                 compressed
 normal    Z
 TIME      TIME                12mr   16-JAN 06:00         16-DEC 01:20        full

The longitude and latitude axes still have their full range, because of their dependence on SST so they should not be listed as compressed.

[AnsleyManke]

This is related to the fix for issue #1916. That bug came from RETURN= evaluations, and involved a fix there. The same logic needs to be applied to SHOW GRID. In both cases we're getting information about the grids of user-defined variables without loading those variables into memory.

Fix in show_grid.F and a new script err751_show_grid_expr.jnl

In the benchmarks there are some differences in a few scripts related to dynamic grids and the output of SHOW GRID/DYNAMIC. These changes are fine.