testsuite: add test for kcmdline params with no value

Use "modprobe -c" to dump the configuration. Since we configure our
rootfs to have only a /proc/cmdline file, this should dump the knowledge
we have from its parsed content.

Test if <module>.option, without any value is correctly parsed, as fixed
in commit 493dc65 ("libkmod: Fix getting param with no value from kcmdline")
testsuite: give a more suitable description to test

We are not only checking if those options are correctly parsed from
kcmdline, but if in fact they are being passed to the final
(f)init_module call. This is why we use 'modprobe --show-depends'
instead of the simpler 'modprobe -c'.
testsuite: add test to ignore unrelated strings in kcmdline

Strings unrelated to modules and modprobe should be ignored and not
appear in the output of "modprobe -c".

This adds a test for the fix provided in aa87854 ("libkmod-config: Only
match dot before '=' in /proc/cmdline").
testsuite: add test for '.' correctly parsed in param's value

In kcmdline it's possible to have a dot in the param's value. The
support for this was added in 66f3228 ("libkmod: Add support for '.' in
module parameter on kcmdline") and is needed to correctly support some
modules that depend on it.

This test was added in order to make sure the commit  aa87854
("libkmod-config: Only match dot before '=' in /proc/cmdline") didn't
break it. Although that commit  message says it's allowing to match a
dot before '=' it's actually enforcing the first part of the string to
be always in the format "<module-name>.param". Dots after '=' are still
correctly allowed.
build-sys: add small redirecting Makefiles

These redirecting makefiles simplifies compiling from some editors and
when CWD is not the root of the source tree. This is similar to what was
introduced in systemd in 340d89e ("build-sys: add small redirecting
Makefiles to simplify compilation from within emacs")
build-sys: Do not require xsltproc for installation of man pages

Same reason as found in this commit to systemd:

	commit 4ca39b280fce3c60d2fdecbd478fd9bf7f9d3e64
	Author: Mike Gilbert <floppym@gentoo.org>
	Date:   Sun Feb 23 11:21:13 2014 -0500

	    configure: Do not require xsltproc for installation of man pages

	    The release tarballs ship with pre-generated man pages, so we do not
	    need xsltproc for a typical end-user build.

	    Developers will probably have xsltproc anyway, but if not they will now
	    encounter a build-time failure instead of an error in configure.
man: clarify the support to modules.dep file
man: use systemd as example instead of udev

Nowadays udev doesn't create nodes in /dev anymore. This role is rather
taken by systemd-tmpfiles on early boot so reference it generically as
systemd.