IMPORTANT: Corrected few typos and updated nesting.F

[arango]

This is a simple update:

• Added make configuration Darwin-nag.mk, which allows compiling/linking ROMS with the NAGFOR compiler on Apple Silicon (Arm v8 processor) Macs. In addition, we corrected several minor typos that the NAGFOR compiler didn't like. Many thanks to David Robertson for getting this to work.

• Corrected typos in gls_corstep.F and lmd_vmix.F routines. Many thanks to Michael Dinniman for ​reporting this issue.

• Corrected bug in get_grid.F when the UV_DRAG_GRID and PIO_LIB library C-preprocessing options are activated. Many thanks to Pan Feng for ​bringing this issue to our attention.

• Corrected typo in equilibrium_tide.F. Many thanks to Pan Feng for ​reporting this problem.

• Updated nesting.F to ensure that the averaged zeta in the donor grid is not less than Dcrit when WET_DRY is activated. Introduced a REFINE_BOUNDARY C-preprocessing option to suppress updating u, v, ubar, and vbar in fine2coarse. The default is to REFINE_BOUNDARY off. Many thanks to John Warner for the update.