Fix FindRS(3) modules

A FindFoobar module must not include a UseFoobar file. CGAL_UseRS3 now
includes CGAL_UseMPFI, and not FindRS and FindRS3.

+ Fix also a typo in a message of FindRS3.

Installation/cmake/modules/CGAL_UseRS3.cmake

@@ -40,6 +40,8 @@ if( RS3_FOUND AND NOT RS3_SETUP )
       message( STATUS "Using old RS signatures" )
     endif( RS3_OLD_INCLUDES )
 
+    include(CGAL_UseMPFI)
+
   set (RS3_SETUP TRUE)
 
   endif( RS3_FOUND AND NOT RS3_SETUP )

Installation/cmake/modules/FindRS.cmake

@@ -12,7 +12,6 @@ endif()
 if( MPFI_FOUND )
 
   include( CGAL_VersionUtils )
-  include( ${MPFI_USE_FILE} )
 
   find_path(RS_INCLUDE_DIR
             NAMES rs_exports.h

Installation/cmake/modules/FindRS3.cmake

@@ -9,8 +9,6 @@ if ( RS_FOUND )
 
 if( MPFI_FOUND )
 
-  include( ${MPFI_USE_FILE} )
-  include( ${RS_USE_FILE} )
   include( CGAL_VersionUtils )
 
   find_path(RS3_INCLUDE_DIR
@@ -68,9 +66,9 @@ else( MPFI_FOUND )
 
 endif( MPFI_FOUND )
 
-else( RS3_FOUND )
+else( RS_FOUND )
 
-  message( STATUS "RS3 requires MPFI" )
+  message( STATUS "RS3 requires RS" )
   set( RS3_FOUND FALSE )
 
 endif( RS_FOUND )