FreeBSD/src ae3aa14 (r346471)sbin/reboot boot_i386.8, stand/man loader.8

MFC r333662: Clarify that boot_mute / boot -m mutes kernel console only

Perhaps RB_MUTE could mute user startup (rc) output as well, but right
now it mutes only kernel console output, so make the documentation match
reality.

PR:             228193
DeltaFile
+2-2sbin/reboot/boot_i386.8
+2-2stand/man/loader.8
+4-42 files

UnifiedSplitRaw