FindSWIG: Use NAMES in find_program directives (#12280)

Without this, regular swig (not 2.0) executable is not found
automatically.

Commit 55b7c87e (Add support for new swig 2.0 application, 2011-03-28)
added support for finding swig 2.0 at the (accidental) expense of not
finding 1.x.  Fix this regression.

Modules/FindSWIG.cmake

@@ -27,7 +27,7 @@
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
 
-FIND_PROGRAM(SWIG_EXECUTABLE swig2.0 swig)
+FIND_PROGRAM(SWIG_EXECUTABLE NAMES swig2.0 swig)
 
 IF(SWIG_EXECUTABLE)
   EXECUTE_PROCESS(COMMAND ${SWIG_EXECUTABLE} -swiglib