mount: add ext4 to some places to the man page

sys-utils/mount.8

@@ -930,7 +930,7 @@ output for extN filesystems).
 The following options apply to any filesystem that is being
 mounted (but not every filesystem actually honors them \(en e.g.\&, the
 .B sync
-option today has an effect only for ext2, ext3, fat, vfat and ufs):
+option today has an effect only for ext2, ext3, ext4, fat, vfat and ufs):
 
 .TP
 .B async
@@ -966,7 +966,8 @@ The
 .B context=
 option is useful when mounting filesystems that do not support
 extended attributes, such as a floppy or hard disk formatted with VFAT, or
-systems that are not normally running under SELinux, such as an ext3 formatted
+systems that are not normally running under SELinux, such as an ext3 or ext4 formatted
+
 disk from a non-SELinux workstation.  You can also use
 .B context=
 on filesystems you do not trust, such as a floppy.  It also helps in compatibility with
@@ -2364,7 +2365,7 @@ not specified or the filesystem is known for libblkid, for example:
 .sp
 .B "mount /tmp/disk.img /mnt"
 .sp
-.B "mount \-t ext3 /tmp/disk.img /mnt"
+.B "mount \-t ext4 /tmp/disk.img /mnt"
 .sp
 .RE
 This type of mount knows about three options, namely
@@ -2518,7 +2519,7 @@ It is possible for a corrupted filesystem to cause a crash.
 .PP
 Some Linux filesystems don't support
 .BR "\-o sync " nor " \-o dirsync"
-(the ext2, ext3, fat and vfat filesystems
+(the ext2, ext3, ext4, fat and vfat filesystems
 .I do
 support synchronous updates (a la BSD) when mounted with the
 .B sync