buildsys: replace autotools with plain makefiles

buildsys: replace autotools with plain makefiles

pve-cluster is not a big project with to much dependencies, so
autotools was a bit of an overkill for it.
Omit it, plus a ./configure step in general and just use a plain
Makefile - in combination with pkg-config - like we do in our other
projects.

Build time gets reduced quite a bit - albeit the were never that big
anyway...:

(old autotools) time make deb
make deb  12.96s user 1.78s system 94% cpu 15.543 total

(new plain makefile) time make deb
make deb  9.40s user 1.14s system 100% cpu 10.465 total

A third less time needed here, and with compiling in parallel I can
shave off even 1.5 seconds more, so almost  half of the original
time.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>