src: support for selectors with different byteorder with interval concatenations

src: support for selectors with different byteorder with interval concatenations

Assuming the following interval set with concatenation:

 set test {
	typeof ip saddr . meta mark
	flags interval
 }

then, the following rule:

 ip saddr . meta mark @test

requires bytecode that swaps the byteorder for the meta mark selector in
case the set contains intervals and concatenations.

 inet x y
   [ meta load nfproto => reg 1 ]
   [ cmp eq reg 1 0x00000002 ]
   [ payload load 4b @ network header + 12 => reg 1 ]
   [ meta load mark => reg 9 ]
   [ byteorder reg 9 = hton(reg 9, 4, 4) ] 	<----- this is required !
   [ lookup reg 1 set test dreg 0 ]

This patch updates byteorder_conversion() to add the unary expression
that introduces the byteorder expression.

Moreover, store the meta mark range component of the element tuple in
the set in big endian as it is required for the range comparisons. Undo
the byteorder swap in the netlink delinearize path to listing the meta
mark values accordingly.

Update tests/py to validate that byteorder expression is emitted in the
bytecode. Update tests/shell to validate insertion and listing of a
named map declaration.

A similar commit 806ab081dc9a ("netlink: swap byteorder for
host-endian concat data") already exists in the tree to handle this for
strings with prefix (e.g. eth*).

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>