deb-pkg: s/hdr/kernel_headers_/ && s/header/libc_headers_/

hdrpackage and headerpackage are not intuitive names,
use proposed alternatives by Michel Marek.

While touching them move the mkdir of the kernel_headers dir up
and fix it for paranoid umask.

CC: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: maximilian attems <max@stro.at>
Signed-off-by: Michal Marek <mmarek@suse.cz>