Revision 318490

MFC r317803:

Enable automounting of exFAT media.

With fstyp(8) being updated to detect exfat in base r312003, it seems
like a good time to add support for auto-mounting SDXC cards -- which
use exfat by default.

The user will need to locally compile and install sysutils/fusefs-exfat
for this to succeed; logs a message to that effect when not installed.

PR:		218743
Submitted by:	eborisch+FreeBSD@gmail.com