readahead: chunk on spinning media

Readahead has all sorts of bad side effects depending on your
storage media. On rotating disks, it may be degrading startup
performance if enough requests are queued spanning linearly
over all blocks early at boot, and mount, blkid and friends
want to insert reads to the start of these block devices after.

The end result is that on spinning disks with ext3/4 that udev
and mounts take a very long time, and nothing really happens until
readahead is completely finished.

This has the net effect that the CPU is almost entirely idle
for the entire period that readahead is working. We could have
finished starting up quite a lot of services in this time if
we were smarter at how we do readahead.

This patch sorts all requests into 2 second "chunks" and sub-sorts
each chunk by block. This adds a single cross-drive seek per "chunk"
but has the benefit that we will have a lot of the blocks we need
early on in the boot sequence loaded into memory faster.

For a comparison of how before/after bootcharts look (ext4 on a
mobile 5400rpm 250GB drive) please look at:

    http://foo-projects.org/~sofar/blocked-tests/

There are bootcharts in the "before" and "after" folders where you
should be able to see that many low-level services finish 5-7
seconds earlier with the patch applied (after).
readahead: cleanups

- check for OOM
- no need to use floats and round()
man: network.target is also a passive target
units: automatically order all mount units after network.target

Previously it was necessary to pull in remote-fs-pre.target to order the
mount units against network.target since the ordering was done
transitively via remote-fs-pre.target.

As network implementations shouldn't need to know about the specific
use-case of network mounts we instead now simply order network.target
against all mounts too. This should make it unnecessary for network
managing services to import remote-fs-pre.target explicitly, as
network.target will now suffice.
Simplify the meaning of %s

The rules governing %s where just too complicated. First of
all, looking at $SHELL is dangerous. For systemd --system,
it usually wouldn't be set. But it could be set if the admin
first started a debug shell, let's say /sbin/sash, and then
launched systemd from it. This shouldn't influence how daemons
are started later on, so is better ignored. Similar reasoning
holds for session mode. Some shells set $SHELL, while other
set it only when it wasn't set previously (e.g. zsh). This
results in fragility that is better avoided by ignoring $SHELL
totally.

With $SHELL out of the way, simplify things by saying that
%s==/bin/sh for root, and the configured shell otherwise.
get_shell() is the only caller, so it can be inlined.

Fixes one issue seen with 'make check'.
tests: fix size_t in format string
tests: skip bus test if bus cannot be opened

To make the result more visible, special return value
is used to tell automake that the test was skipped. While
at it, use the same return value in other skipped tests.
keymap: Fix Touchpad Toggle on MSI Wind U90/U100

This key is handled by the hardware already, so handling it again in software
nullifies the effect. Newer kernels read the real state and send out a separate
KEY_TOUCHPAD_ON or KEY_TOUCHPAD_OFF event, so in both cases we need to ignore
that key.

https://bugs.freedesktop.org/show_bug.cgi?id=62404
bootctl: rename status output header
core: check return value of rm_rf_dangerous and warn if it fails
shared: free dt (temporary dir name) on fail

[zj: modified to not to try to rmdir() dir we haven't created.]
systemd-sysctl: Handle missing /etc/sysctl.conf properly

Since fabe5c0e5fce730aa66e10a9c4f9fdd443d7aeda, systemd-sysctl returns
a non-zero exit code if /etc/sysctl.conf does not exist, due to a
broken ENOENT check.
sd-bus: check c->path for null instead of path
log: fix error codes handling in catalog_list_items

It does not make sense to print error code from previous loop.
catalog: fix error codes handling in catalog_list_items

Previously r was set to zero and so if(r<0) was never true.
man/os-release: Add BUILD_ID field

BUILD_ID is a fairly generic field used to identify the system image
that was used to install the distribution.
bootctl: Binary: --> File:
bootctl: ESP --> Partition
build-sys: fix HAVE/ENABLE_FIRMWARE

https://bugs.freedesktop.org/show_bug.cgi?id=62864
hwdb: update