Finish the alltypes_pointer testcase, use valgrind if available.

tests/SConstruct

@@ -59,11 +59,6 @@ if not env.GetOption('clean'):
         if stddef: conf.env.Append(CPPDEFINES = {'HAVE_STDDEF_H': 1})
         if string: conf.env.Append(CPPDEFINES = {'HAVE_STRING_H': 1})
     
-    # Check if we have mallinfo for memory leak tests
-    mallinfo = conf.CheckFunc('mallinfo', '#include <malloc.h>\n')
-    if mallinfo:
-        conf.env.Append(CPPDEFINES = {'HAVE_MALLINFO': 1})
-    
     # Check if we can use pkg-config to find protobuf include path
     status, output = conf.TryAction('pkg-config protobuf --variable=includedir > $TARGET')
     if status: