[Bug-stow] manual: use of prefix redirection @ make install time vs DESTDIR

[Claudio Fontana]

Hello,

I quickly read through the stow manual, the chapter about how
to configure/install software from source for later use with
stow.

I think that a better course of action at make install time is
to just let the prefix be, (no prefix= redirection) and instead use
DESTDIR for the staged installation.

http://www.gnu.org/prep/standards/standards.html#DESTDIR

DESTDIR has good support in most GNU packages (emacs included btw),
so maybe the manual could be updated to cite DESTDIR?

Thank you,

Claudio