Example link command in documentation out of date

[rgmiller]

Describe the problem you're observing

The dynamic linking example in the docs shows linking C code against libunifyfs_gotcha.so instead of libunifyfs_mpi_gotcha.so. (See https://unifyfs.readthedocs.io/en/latest/link.html) The Fortran example probably needs to be updated, too.

[rgmiller]

Also, the example for dynamic linking Fortran code doesn't include -lgotcha. Should it?