MFC r281787

dmesg: accommodate message buffer growth between the sysctl calls

Allocate 12.5% extra space to avoid ENOMEM when the message buffer
is growing steadily.

Reported by: Steve Wahl <steve_wahl@dell.com> (and tested)
Sponsored by: Dell Inc.

MFC r281787

dmesg: accommodate message buffer growth between the sysctl calls

Allocate 12.5% extra space to avoid ENOMEM when the message buffer
is growing steadily.

Reported by: Steve Wahl <steve_wahl@dell.com> (and tested)
Sponsored by: Dell Inc.