datatype: Replace getnameinfo() by internal lookup table

datatype: Replace getnameinfo() by internal lookup table

To avoid exceeding the inputs number limit of the flex scanner used,
when calling getnameinfo() in inet_service_type_print().

The new symbol_table was associated with inet_service_type, to enable
listing all pre-defined services using nft command line tool.

The listed services are all well-known and registered ports of my
local /etc/services file, from Ubuntu 16.04. Service numbers are
converted to respect network byte order.

Signed-off-by: Elise Lennion <elise.lennion@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>