Merge branch 'develop' of github.com:ChaiScript/ChaiScript into develop

include/chaiscript/language/chaiscript_engine.hpp

@@ -36,7 +36,9 @@
 #else
 #ifdef CHAISCRIPT_WINDOWS
 #define VC_EXTRA_LEAN
+#if !defined(WIN32_LEAN_AND_MEAN)
 #define WIN32_LEAN_AND_MEAN
+#endif
 #include <windows.h>
 #endif
 #endif

include/chaiscript/language/chaiscript_eval.hpp

@@ -436,6 +436,7 @@ namespace chaiscript
           else if (this->children[1]->text == ":=") {
             if (lhs.is_undef() || Boxed_Value::type_match(lhs, rhs)) {
               lhs.assign(rhs);
+              lhs.reset_return_value();
             } else {
               throw exception::eval_error("Mismatched types in equation");
             }