xt: Print comment match data as well

xt: Print comment match data as well

In order to translate comment matches into the single nftables rule
comment, libxtables does not immediately (maybe mid-rule) print a
comment match's string but instead stores it into struct
xt_xlate::comment array for later.

Since xt_stmt_xlate() is called by a statement's .print callback which
can't communicate data back to caller, nftables has to print it right
away.

Since parser_bison accepts rule comments only at end of line though, the
output from above can't be restored anymore. Which is a bad idea to
begin with so accept this quirk and avoid refactoring the statement
printing API.

Signed-off-by: Phil Sutter <phil@nwl.cc>