build-sys: use recipe for moving libs

Just avoids repeating the same code a few times.
The way that hooks are named is standardized.
No functional change.
build-sys: use VALGRIND not __OPTIMIZE__ as condition for valgrind compat

Actually, one might want to run valgrind even on optimized code.
Now the same check is used in the jenkins hash functions and
hashtable.
core/manager: modernize style
core/dbus-unit: modernize style
core/mount: modernize style
core/path: modernize style
fstab-generator: modernize style
journal: new logging macros to include UNIT=

Adding UNIT= to log lines allows them to be shown
in 'systemctl status' output, etc.

A new set of macros and functions is added. This allows for less
verbose notation than using log_struct() explicitly.

The set of logging functions is expanded to take a pair of arguments
(e.g. "UNIT=" and the RHS) which add an extra line to the structured
log entry. This can be used to add macros which add a different
identifier later on.
systemd: use unit logging macros
update TODO