build: use -ftrapv for development

We want to find these bugs if they exist.
man: beef up ExecStart description

We have lots of questions from people who assume that shell syntax works
here, so let's be very explicit what is allowed and what is not. A few
examples should also help.

http://bugs.debian.org/732156
man: remove advice to avoid setting the same var more than once

So far the compatibility with .desktop settings hasn't been imporant
at all, and we do not want people to write convoluted unit
files.
systemctl: add the --plain option to the help message
test-journal-syslog: use streq_ptr since we pass in NULL
bus: return negative errno on error

https://bugs.freedesktop.org/show_bug.cgi?id=72688
udev-builtin-path: fix printf specifiers
bus: update kdbus monitoring interface
bus: _printf_ attributes should be on prototypes not function definitions for non-static functions
Fix a few resource leaks in error paths

https://bugzilla.redhat.com/show_bug.cgi?id=1043304
Fix a few signed/unsigned format string issues

Since numbers involved are all small, behaviour was correct already.

https://bugzilla.redhat.com/show_bug.cgi?id=1043304
build-sys: add cppcheck target

This uses --enable=all mode. Should be taken with a grain of salt
though. While many recommendations make sense we should probably keep
"int r" always on function scope, and many of the portability warnings
really don't matter to us because we only care for Linux/glibc.
Fix segv introduced by 2fd069b18e525860514a70d3ea08410ca122d3e2

n->path is pointing to the value now, we set s = NULL above.
build-sys: warn if builds are not byte-by-byte reproducible due to usage of __DATE__ and suchlike
core: refuse doing %h, %s, %U specifier resolving in PID 1

These specifiers require NSS lookups to work, and we really shouldn't do
them from PID 1 hence. With this change they are now only supported for
user systemd instance, or when the configured user for a unit is root.
catalog: fix language detection

Detection would fail if language was not specified in the filename
but a dot appeared somewhere higher in the path.
util: try harder to increase the send/recv buffers of sockets

If we have the priviliges we will try SO_SNDBUFFORCE/SO_RCVBUFFORCE and
only fall back to SO_SNDBUF/SO_RCVBUF if that fails.
update TODO
bus: increase the bus socket buffer to 8 MB similar, to the log socket buffers
rtnl: add support for receiving route messages