Cleanup: rename edge-ring preselect file

Having all pre-selection in one file isn't so nice,
differentiate edge-ring from element pre-selection.

source/blender/editors/mesh/CMakeLists.txt

@@ -57,7 +57,7 @@ set(SRC
 	editmesh_loopcut.c
 	editmesh_path.c
 	editmesh_polybuild.c
-	editmesh_preselect.c
+	editmesh_preselect_edgering.c
 	editmesh_preselect_elem.c
 	editmesh_rip.c
 	editmesh_rip_edge.c

source/blender/editors/mesh/editmesh_preselect_edgering.c

@@ -18,7 +18,7 @@
  * ***** END GPL LICENSE BLOCK *****
  */
 
-/** \file blender/editors/mesh/editmesh_preselect.c
+/** \file blender/editors/mesh/editmesh_preselect_edgering.c
  *  \ingroup edmesh
  */