lib: Merge libmisc into libshadow

lib: Merge libmisc into libshadow

The separation was unnecessary, and caused build problems.  Let's go
wild and obliterate the library.  The files are moved to libshadow.

Scripted change:

$ find libmisc/ -type f \
| grep '\.[chy]$' \
| xargs mv -t lib;

Plus updating the Makefile and other references.  While at it, I've
sorted the sources lists.

Link: <https://github.com/shadow-maint/shadow/pull/792>
Reported-by: David Seifert <soap@gentoo.org>
Cc: Sam James <sam@gentoo.org>
Cc: Christian Bricart <christian@bricart.de>
Cc: Michael Vetter <jubalh@iodoru.org>
Cc: Robert Förster <Dessa@gmake.de>
[ soap tested the Gentoo package ]
Tested-by: David Seifert <soap@gentoo.org>
Acked-by: David Seifert <soap@gentoo.org>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Iker Pedrosa <ipedrosa@redhat.com>
Acked-by: <lslebodn@fedoraproject.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>