barrier: initalize file descriptors with -1

Explicitly initalize descriptors using explicit assignment like
bus_error. This makes barriers follow the same conventions as
everything else and makes things a bit simpler too.

Rename barier_init to barier_create so it is obvious that it is
not about initialization.

Remove some parens, etc.
resolved: do not use unitialized variable
compress: fix return value
man,journal: add note about sd_journal_get_cutoff_monotonic_usec return value

Also modify the function itself to be a bit simpler to read.
machinectl: make sure we are not reading an unitialized variable
Makefile.am: tweaks to python commands
Nuke update-kbd-map

Our version has evolved independently of the original table
in systemd-config-keyboard, so it cannot be ever regenerated from
original upstream. Remove script to avoid confusion.
Be more verbose when bind or listen fails

Also be more verbose in devnode_acl_all().
Small modernizations
core: show timeouts when watchdog howls
barrier: suppress false-positive warning

If poll() returns, one of both revents must be set, thus "buf" is set by
either clause. This is non-obvious for code-checkers so add an "else
continue;" clause to suppress "uninitialized variable" warnings.
Refuse mount on symlink