timesyncd: fix error path return value

https://bugs.freedesktop.org/show_bug.cgi?id=78752
Update TODO
core: make sure to serialize jobs for all units

Previously we wouldn't serialize jobs for units that themselves have
nothing to serialize.

http://lists.freedesktop.org/archives/systemd-devel/2014-May/019051.html
man: clarify that the ExecReload= command should be synchronous

http://lists.freedesktop.org/archives/systemd-devel/2014-May/019054.html
timesyncd: fix typo in comment
networkd: rename Address and Route list fields
networkd: fix typo
TODO
networkd: log the initialization status of links
Revert "networkd: order after udev kernel socket"

This reverts commit a555350d47c4b70d716a63424933b34902c98300.

This did not fix the problem, just made it harder to hit.
network: always create /run/systemd/network/links

This ways the networkd client library should work even if networkd is
not running.

http://lists.freedesktop.org/archives/systemd-devel/2014-May/019242.html
build-sys: at configure check for verifying that ln supports --relative
man: fix some minor language typos
readahead: modernizations
man: readahead: fix cmdline switch inconsistency between readahead.c and docs

Source code has "files-max" and XML has --max-files.
networkd: hardcode a set of default dns servers

Similarly to NTP servers, this can be set at compile-time.
fsck: Allow to specify the fsck repair option in the cmdline

Some unattended systems do not have a console attached and entering
the default rescue mode will not be too helpful. Allow to specify
the "-y" option to attempt to fix all filesystem errors.

Manually verified by downloading an image.gz of e2fsprogs, using
losetup and running systemd-fsck on the loop device and varying
the fsck.repair=preen|yes|no option.
path-util: add path_make_relative()

In user_dirs() in path-lookup.c, I want to replace this:
        symlink("../../../.config/systemd/user", data_home);
with
        symlink(config_home, data_home);
to avoid hardcoding .config when XDG_CONFIG_HOME is set.

The problem is that config_home is an absolute path, and it's better
to make the symlink relative. path_make_relative() is an utility
function that converts an absolute path into a relative one.
path-lookup: don't hardcode .config

If XDG_CONFIG_HOME is set, then we should respect that.
man: update journald rate limit defaults

This brings the man page back into sync with the actual code.