This patch fixes compiler warnings like the following:
./lib/ovsdb-types.h:171:5: error: comparison of unsigned expression
>= 0 is always true [-Werror=type-limits]
This function only worked properly inside OVSDB itself, because that is
the only place where the 'refTable' member of ovsdb_base_type is set.
Both inside and outside OVSDB, 'refTableName' is set for reference types,
so it's better to check for that.
This doesn't fix any existing bug because this function was only used
inside OVSDB until now.
Some of the uses for the formerly supported regular expression constraints
were simply to limit values to those in a set of allowed values.
This commit adds support for that kind of simple enumeration constraint.
Regular expression constraints have caused nothing but trouble due to the
lack of a ubiquitous regular expression library. PCRE is *almost*
everywhere, but it has different versions, and different features, and
different bugs, in different places. It is more trouble than it is worth.
So this commit drops support.
