Don't umount anything more than the loopback image itself to avoid
problems with:
 - udev (fixes #4913)
 - apk cache
 - setup-bootable -u

I also added perl-net-libidn as a depends as recommended by the
module's build script:
-----------------------------------------------------------------
WARNING
No library for handling international domain names found.
It will work but croak if you try to verify an international name
against a certificate. It's recommended to install either
Net::IDN::Encode, Net::LibIDN or URI version>=1.50
-----------------------------------------------------------------

It is only used by main/avahi and this package creates the group and
user on demand in its .pre-install script.

main/alpine-conf: Change /etc/lbu/lbu.conf permissions to 644. Filesystems creation fixes and description added in setup-disk script.

01-16: committed to upstream
17: GH #331
18: GH #332
19: GH #333

main/btrfs-progs: All binaries and scripts not involved in the boot process and the creation of the filesystem are moved to -extra subpackage

TODO:
- replace /sbin/fsck.btrfs dummy script to real '/sbin/btrfs check'-based one.

main/xfsprogs: All binaries and scripts not involved in the boot process and the creation of the filesystem are moved to -extra subpackage

TODO:
- replace /sbin/fsck.xfs dummy script with real '/sbin/xfs_repair'-based one.

main/e2fsprogs: All binaries and scripts not involved in the boot process and the creation of the filesystem are moved to -extra subpackage

main/e2fsprogs: libraries moved to -libs subpackage. libcomm_err development scripts and data moved from main package to -dev subpackage

- remove unnecessary parameters in ./configure & make install
- don't know why libraries was in -dev subpackage. Move it to -libs subpackage

Makes debugging easier.