meson: introduce meson, covering libkmod.so

meson: introduce meson, covering libkmod.so

The meson build system has been getting popularity, but for us that
means coverage and sanitisers OOTB et al.

The current patch, handles only libkmod.so and libkmod.pc. The rest will
follow-up.

Notable changes comparing against the autoconf:
 - more consistent dirnames
 - omit printing bash completion dir and compiler flags from summary
 - debug toggle is renamed to debug-messages
 - a few [C,LD]FLAGS were omitted - they're provided by meson itself
 - libkmod.pc has the more complete Requires.private over Libs.private
 - use the symver for libkmod.so, omit the version-info magic

Note: The minimal meson version is 0.60.0 akin to systemd and mesa.

v2:
 - use gnu11, list both LGPL and GPL licenses
 - add meson files to EXTRA_DIST
 - add temporary stdndupa workaround
 - move kmod bash-completion to later patch

v3:
 - switch to meson 0.60.0
 - remove stdndupa workaround

Loosely based on the work by: Dave Reisner <dreisner@archlinux.org>

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/86
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>