Whitespace cleanup of all Makefiles*

- some of the %.clean rules in the test-suite Makefiles were using a single tab
  as an empty rule, dangerous! I've replaced these with the safer '@exit 0'.

Examples/test-suite/perl5/Makefile.in

@@ -31,7 +31,7 @@ include $(srcdir)/../common.mk
 # none!
 
 # Rules for the different types of tests
-%.cpptest: 
+%.cpptest:
 	$(setup)
 	+$(swig_and_compile_cpp)
 	$(run_testcase)
@@ -41,7 +41,7 @@ include $(srcdir)/../common.mk
 	+$(swig_and_compile_c)
 	$(run_testcase)
 
-%.multicpptest: 
+%.multicpptest:
 	$(setup)
 	+$(swig_and_compile_multi_cpp)
 	$(run_testcase)