Add excludefs config option to mount module

Adds a configuration option (currently hidden) to allow the distro to
hide certain filesystems from the mount module within Webmin (e.g. /dev)
since these shouldn't be modified from the web interface.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

Upstream-status: Pending

--- webmin-1.570.orig/mount/index.cgi
+++ webmin-1.570/mount/index.cgi
@@ -33,10 +33,12 @@ elsif ($config{'sort_mode'} == 1) {
 	}
 
 # Build visible filesystems list
+@excludefs = split(/,/, $config{excludefs});
 foreach $m (@all) {
 	@minfo = @$m;
 	$p = &simplify_mount_path($minfo[0], $minfo[2]);
 	next if ($ignore{$minfo[2]});
+	next if (grep {$_ eq $minfo[2]} @excludefs);
 	@mmodes = &mount_modes($minfo[2], $minfo[0], $minfo[1]);
 	$canedit = $can_edit{$minfo[2]} && !$mmodes[4] &&
             	   &can_edit_fs(@minfo);