make a Makefile.common for linux-modutils and use it

build dependencies: ranlib, ar, bison, flex

/lib/modules/ is hard-coded in man pages and code

should linux-kernel and modutils be in same pkgsrc category?

provide better example of modules.conf

It would be nice if pkgsrc would provide an automatically generated
MESSAGE about how to enable the rc.d script.

Maybe have a MESSAGE about setting up ${PKG_SYSCONFDIR}/modules
for boot-time.

maybe a different HOMEPAGE should be used

no rc.d script
