Makefiles: protect from % rules, don't rebuild

GNU make tries to rebuild any makefiles it uses. While in general it's
a good idea (and it is used e.g. in autoconf-based builds), in our case
it is not necessary, as all the makefiles are static.

More to say, as we have a few "match anything" rules for subdirectories,
Makefiles in these subdirs are also matching these rules, which leads to
excessive (re)building while a particular makefile is needed.

Protect such Makefiles with explicit (or pattern) rules, so make knows
it should do nothing to rebuild those.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>