There were two specific problems with the logging macros:
1) the existing varargs usage didn't allow for format string checking,
which is bad, since it could make logging segfault if the arguments
don't match the format string
2) it didn't allow logging usage without wrapping {}, ie this didn't work:
if (foo)
nm_log_dbg (...)
blah blah
Fix all that by using the varargs stuff correctly.
Previously the input would simply be printed, but if you're not
changing either the level or domains (ie sending "") then the
unchanged logging domains wouldn't be printed, only "".
Some stuff we build (the DHCP manager) gets built independently
so that we can use it for unit tests. For that, we need to build
the logging bits separately too, since the independent DHCP
library can't use them if they are embedded in NM.
