Improve the endian support for DragonFly by providing functions to convert

Improve the endian support for DragonFly by providing functions to convert
16/32/64 bit variables and parts of byte streams between host order and
big / little endian.

Reduce the namespace pollution for normal usage, e.g. of sys/types.h.
The duplication of ntohl and friends in arpa/inet.h and sys/param.h comes
from byteorder(3) showing sys/param.h as header file and SUS requiring
arpa/inet.h to provide this functions.

Remove local hacks in acpidump and usb_port.h.

The prototype of ntohl and friends is in sync with SUS, warnings e.g. for
implicit sign casts or use of int/long will be handled separately.

Written-by:	Hitten Pandya and Joerg Sonnenberger
Inspired-by:	FreeBSD