Fix some MSVC compiler warnings in the test suite

nested_in_template_wrap.cxx(247): warning C4244: 'initializing': conversion from 'double' to 'int', possible loss of data
python_pybuffer_wrap.cxx(2788): warning C4267: 'return': conversion from 'size_t' to 'int', possible loss of data
Modules\python.cxx(2227) : warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)

Examples/test-suite/python_pybuffer.i

@@ -28,7 +28,7 @@
         ++count;
     return count;
   }
-  int func4(const char *buf4)
+  size_t func4(const char *buf4)
   {
     return strlen(buf4);
   }