GIOLister: ignore system mounts as defined by GIO

Strawberry has some heuristics to exclude things
like the root mount, /boot, tmpfs, etc. from the devices list.

However, it's somewhat incomplete. GIO (GLib component)
has more complete definition of "internal system mounts"
that should not be presented to the user.

Additionally, don't try to query filesystems free/total size
if it's internal, as that triggers automounting for autofs
filesystems (#410).

CMakeLists.txt

@@ -117,6 +117,9 @@ endif()
 pkg_check_modules(GLIB REQUIRED glib-2.0)
 pkg_check_modules(GOBJECT REQUIRED gobject-2.0)
 pkg_check_modules(GIO REQUIRED gio-2.0)
+if(UNIX)
+  pkg_check_modules(GIO_UNIX gio-unix-2.0)
+endif()
 pkg_check_modules(LIBCDIO libcdio)
 pkg_check_modules(GSTREAMER gstreamer-1.0)
 pkg_check_modules(GSTREAMER_BASE gstreamer-base-1.0)
@@ -391,6 +394,11 @@ optional_component(GIO ON "Devices: GIO device backend"
   DEPENDS "Unix or Windows" "NOT APPLE"
 )
 
+optional_component(GIO_UNIX ON "Devices: GIO device backend (Unix support)"
+  DEPENDS "libgio-unix" GIO_UNIX_FOUND
+  DEPENDS "Unix" "UNIX"
+)
+
 optional_component(LIBGPOD ON "Devices: iPod classic support"
   DEPENDS "libgpod" LIBGPOD_FOUND
   DEPENDS "gdk-pixbuf" GDK_PIXBUF_FOUND