match: Single malloc minimatch.

match: Single malloc minimatch.

Allocate the miniflow and minimask in struct minimatch at once, so
that they are consecutive in memory.  This halves the number of
allocations, and allows smaller minimatches to share the same cache
line.

After this a minimatch has one heap allocation for all it's data.
Previously it had either none (when data was small enough to fit in
struct miniflow's inline buffer), or two (when the inline buffer was
insufficient).  Hopefully always having one performs almost the same
as none or two, in average.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>