MFC r320726, r320727

MFC r320726, r320727

r320726:
Expect :snprintf_float to segfault

This issue started occurring within the past month or so.

PR:   220502
Reported by:  Jenkins (amd64-head job)

r320727:
:snprintf_float: don't blindly set RLIMIT_DATA and RLIMIT_AS to 1 MB -- raise
the limit to 32MB instead.

Require user=root and memory=64MB+ first so one can be reasonably sure that
the test will function appropriately.

MFC with:     r320726
PR:   220502

git-svn-id: svn://svn.freebsd.org/base/stable/10@330520 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f