evaluate: prevent merge of sets with incompatible keys

evaluate: prevent merge of sets with incompatible keys

Its not enough to check for interval flag, this would assert in interval
code due to concat being passed to the interval code:
BUG: unhandled key type 13

After fix:
same_set_name_but_different_keys_assert:8:6-7: Error: set already exists with
different datatype (concatenation of (IPv4 address, network interface index) vs
network interface index)
        set s4 {
            ^^

This also improves error verbosity when mixing datamap and objref maps:

invalid_transcation_merge_map_and_objref_map:9:13-13:
Error: map already exists with different datatype (IPv4 address vs string)

.. instead of 'Cannot merge map with incompatible existing map of same name'.
The 'Cannot merge map with incompatible existing map of same name' check
is kept in place to catch when ruleset contains a set and map with same name
and same key definition.

Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>