modprobe,depmod: deprecate "include", sort config files, warn if they miss .conf

modprobe,depmod: deprecate "include", sort config files, warn if they miss .conf

The "include" directive causes a warning now, because it should not be
used anymore. All user-supplied config file belong into the single
directories /etc/modprobe.d/ and /etc/depmod.d/ and nowhere else.
This allows tools like mkinitramfs to find all files without the current
pain.

Any include directives for /etc/modprobe.d/ and /etc/depmod.d/ themselves
are completely ignored now, they are the default and do not need any
configuration.

The existence of the file /etc/modprobe.conf, /etc/depmod.conf will
cause a warning now, and they should be moved to the single directories
/etc/modprobe.d/ and /etc/depmod.d/.

All /etc/modprobe.d/ and /etc/depmod.d/ files without a ".conf" extension
cause a warning now, the extension will be required in a future release
to make the "can-never-be-complete file name filter" obsolete, which tries
to filter left-over files from editors and package managers.

All files in /etc/modprobe.d/ and /etc/depmod.d/ are sorted alphabetically
now, before they are parsed, to produce predictable results and to no longer
depend on readdir() order.

If the config option "binary_indexes no" is given, all possible ".bin"
files are properly ignored now.

The tests have been updated not to use "include", but put all files
in /etc/modprobe.d/ and have a .conf entension.