expr: fix leak in target and match expressions

Release internal data area for match and target expressions.

==30104== 68 bytes in 1 blocks are definitely lost in loss record 1 of 1
==30104==    at 0x4C2B514: calloc (vg_replace_malloc.c:593)
==30104==    by 0x400C2F: main (nft-expr_match-test.c:65)

Reported-by: Ana Rey Botello <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
build: fix make distcheck

Fix missing files that were not included in the tarball
that distcheck generates.

This also includes AC_EXEEXT, otherwise configure complains about
undefined CHECK_GCC_FVISIBILITY.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
expr: match: fix wrong flag setting in nft_rule_expr_match_parse

Expression flags were incorrectly set.

Reported-by: Ana Rey Botello <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>