[PATCH] Improve the compilation-time settings interface

[PATCH] Improve the compilation-time settings interface

Describe variables which make itself takes and adjusts compilation
accordingly (MOZILLA_SHA1, NO_OPENSSL, PPC_SHA1), and make adding
defines more convenient through the $DEFINES variable. $COPTS includes
-g as well now and is not overriden if it was already declared in the
environment. Also, $CFLAGS is appended to rather than reset, so that if
there was already a $CFLAGS environment variable, it's appended to. Some
more variables are also made overridable through the environment. Renamed
$bin to $bindir which is the name commonly used for this.

This is part of the Cogito Makefile changes port.

Signed-off-by: Petr Baudis <pasky@ucw.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>