Negative switches are a bad un-normalized thing. We alerady have some,
but we should try harder to avoid intrdoucing new ones.
Hence, instead of adding two switches:
--foobar
--no-foobar
Let's instead use the syntax
--foobar
--foobar=yes
--foobar=no
Where the first two are equivalent. The boolean argument is parsed
following the usual rules.
Change all new negative switches this way.
This patch also properly aligns the --help table, so that single char
switches always get a column separate of the long switches.
Special care is needed so that we get an error message if the
file failed to parse, but not when it is missing. To avoid duplicating
the same error check in every caller, add an additional 'warn' boolean
to tell config_parse whether a message should be issued.
This makes things both shorter and more robust wrt. to error reporting.
Previously existing scheme where the file name would be based on
the source was just too ugly and unpredicatable. Now there are
only two options:
1. just one file (until rotation),
2. one file per source host, using the hostname as filename part.
For the cases where the source is specified by the user, only
option one is allowed, and the full of the file must be specified.
