GDB MI Reverse Commands added [2 of 3]

[Jakob Engblom]

> > + If the @samp{--reverse} option is specified, resumes reverse execution
> > + of the inferior program, stopping at the previous instruction. If the
> > + previously executed instruction was a return from another instruction,
>                                                       ^^^^^^^^^^^^^^^^^^^
> "another instruction" or "another function"?

Function. There was also the same mistake in the documentation for the CLI
command "reverse-nexti". Fixed it there too.

/jakob