If there are multiple NM_CON_DEFAULT() mentionings on the same line,
previously the script would not parse them all. Adjust, by first wrapping
the line.
Add a new CON_DEFAULT() macro that places a property name into a
special section used at runtime to check whether it is a supported
connection default.
Unfortunately, this mechanism doesn't work for plugins so we have to
enumerate the connection defaults from plugins in the daemon using
another CON_DEFAULT_NOP() macro.
