bug#17722: Makefile rule fix and cleanup patches

[Paul Eggert]

Jim Meyering wrote:
> using scripts for egrep and fgrep may be removed

Let's not remove the scripts, as they're better on platforms where 
they're supported.  Users of a script can more-easily understand and 
modify what it does, which is a better match for the GNU project's 
overarching goals.

Instead, we should use scripts on GNUish platforms, and fall back on 
binary executables only on platforms that don't have a working shell.