Remove references to systemd from the bash completion file

And restore the original LGPL disclaimer text.
Add gitignore to module playground
man: fixup spacing/parens in modprobe.d(5)
depmod: Make dependency loops be fatal

Since the beginning depmod just warned about dependency loops and upon
creation of modules.dep{,.bin} it skipped the modules that were part of
a loop. However just skipping the modules may come as a surprise to
kernel module developers: they will need to try to load the module (or
to pay attention to the log messages) to notice thavt the module has not
been put in the index. Also, differently from module-init-tools we were
not skipping modules that depend on modules with dependency loops,
leading to a segfault in depmod.

So this is a summary of the change in behavior with this patch:

Loop 1)
    A -> B -> C -
    ^           |
    '------------

    Before:
        depmod: WARNING: found 3 modules in dependency cycles!
        depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
        depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
        depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleA.ko in dependency cycle!

        return code: 0

    After:
        depmod: ERROR: Found 3 modules in dependency cycles!
        depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
        depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
        depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleA.ko in dependency cycle!

        return code: 2

Loop 2)
    A -> B -> C -
         ^      |
         '-------

    Before:
        depmod: WARNING: found 2 modules in dependency cycles!
        depmod: WARNING: /tmp/test-kmod//lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
        depmod: WARNING: /tmp/test-kmod//lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
        Segmentation fault (core dumped)

    After:
        depmod: ERROR: Found 2 modules in dependency cycles!
        depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
        depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!

        return code: 2

The segfault above could be fixed, but let's just fail everything
because dependency cycles should be fixed in the modules rather than
just be skipped in the index.
Bail out of index_mm_open() if fstat() fails
Ensure read_long() reads the correct number of bytes from the index
Free realnames if kmod_lookup_alias_from_alias_bin() fails
Free abspath if kmod_module_new_from_path() fails.
Close /sys/module/$NAME directory if opening /proc/module fails.