better guard of IPV6 related stuff
better guard of IPV6 related stuff

Function prototypes are visible whenever IPV6 option is enabled.
Structures and constants are visible either if IPV6 is enabled
or STRICT_HEADERS is disabled.

Signed-off-by: Peter S. Mazinger <1f4071d9f342c1637b13af9bc258f2ff72e96758@gmx.net>

joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc,joel-porquet/tsar-uclibc