fix double free in FXMemoryStream#giveBuffer

The Ruby String buffer was free'd by GC and FXMemoryStream#close

swig-interfaces/FXMemoryStream.i

@@ -57,10 +57,14 @@ public:
 
     /// Give buffer to stream
     void giveBuffer(VALUE str){
+      FXuchar* copy = NULL;
       Check_Type(str,T_STRING);
       FXuchar* buffer=reinterpret_cast<FXuchar*>(StringValuePtr(str));
       FXuval sp=RSTRING_LEN(str);
-      self->giveBuffer(buffer,sp);
+      if( FXMALLOC(&copy, FXuchar *, sp)) {
+        memcpy(copy, buffer, sp);
+        self->giveBuffer(copy,sp);
+        }
       }
   }