CFR: u3g(4) man page tweaks

[Don Lewis]

Document that the u3g driver can be automagically autoloaded by devd
when the device is plugged in.

Also mention that if the driver is not built into the kernel or loaded
before the device is plugged in, then the automatic mode switch does not
happen.

Index: share/man/man4/u3g.4
===================================================================
--- share/man/man4/u3g.4	(revision 258423)
+++ share/man/man4/u3g.4	(working copy)
@@ -18,7 +18,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 8, 2012
+.Dd November 20, 2013
 .Dt U3G 4
 .Os
 .Sh NAME
@@ -40,6 +40,9 @@
 .Bd -literal -offset indent
 u3g_load="YES"
 .Ed
+.Pp
+If neither of the above is done, the driver will automatically be loaded
+by devd when the device is connected.
 .Sh DESCRIPTION
 The
 .Nm
@@ -99,6 +102,10 @@
 .Xr usb 4 ,
 .Xr usb_quirk 4 ,
 .Xr usbconfig 8
+.Sh BUGS
+The automatic mode switch from disk mode to modem mode does not work unless
+the driver is either built into the kernel or loaded before the device is
+connected.
 .Sh HISTORY
 The
 .Nm