Fixed assignment of double to MString.

testing/mstring_test.cpp

@@ -81,6 +81,14 @@ int main(int argc, char **argv) {
 
 //   coreutils::MString test24 = std::endl;
 //   std::cout << "mstring << endl: " << test24 << std::endl;
+
+   coreutils::MString test25 = 3.14159;
+   std::cout << "float: " << test25 << std::endl;
+
+   coreutils::MString test26;
+   double test27 = 4.0f;
+   test26 = test27;
+   std::cout << "float: " << test26 << std::endl;   
    
    return 0;
 }