flow: Fix IPv6 fragment packet handling

IPv6 fragmented packet (except first fragment) will not be handled
correctly. When extracting packet at parse_ipv6(), although nw_frag
should have both of FLOW_NW_FRAG_ANY and FLOW_NW_FRAG_LATER for
later fragment, only FLOW_NW_FRAG_LATER is set.

Signed-off-by: Takashi Kawaguchi <kawaguchi-takashi@mxd.nes.nec.co.jp>
Signed-off-by: Ken Ajiro <ajiro@mxw.nes.nec.co.jp>
Signed-off-by: Jesse Gross <jesse@nicira.com>
INSTALL: Finish sentence about running tests with valgrind.

Signed-off-by: Justin Pettit <jpettit@nicira.com>
ofpbuf: Fix small typo.

Signed-off-by: Justin Pettit <jpettit@nicira.com>