Bumping default data size limit on amd64?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

When testing security/scrypt, the self tests fail with the default
ulimits because one of the test needs 256MB. (After raising the data
size ulimit, the test succeeds.)

Colin Percival suggests that we change the port's defaults here.

DFLDSIZ in arch/amd64/include/vmparam.h was last bumped back in 2004.

He suspects that this would have been increased a long time ago if it
weren't for the fact that malloc allocates pages via mmap.

Anyway, opinions?
 Thomas