Fix Win32 UTF8 marshaling

src/LPUtf8StrMarshaler.cs

@@ -80,7 +80,7 @@ namespace SDL2
 				throw new ArgumentException("ManagedObj must be a string.", "ManagedObj");
 			}
 			var bytes = Encoding.UTF8.GetBytes(str);
-			var mem = Marshal.AllocHGlobal(bytes.Length + 1);
+			var mem = SDL.SDL_malloc((IntPtr) bytes.Length + 1);
 			Marshal.Copy(bytes, 0, mem, bytes.Length);
 			((byte*)mem)[bytes.Length] = 0;
 			return mem;
@@ -94,7 +94,7 @@ namespace SDL2
 		{
 			if (!_leaveAllocated)
 			{
-				Marshal.FreeHGlobal(pNativeData);
+				SDL.SDL_free(pNativeData);
 			}
 		}
 

src/SDL2.cs

@@ -60,6 +60,14 @@ namespace SDL2
 			SDL_TRUE = 1
 		}
 
+		/* malloc/free are used by the marshaler! -flibit */
+
+		[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
+		internal static extern IntPtr SDL_malloc(IntPtr size);
+
+		[DllImport(nativeLibName, CallingConvention = CallingConvention.Cdecl)]
+		internal static extern void SDL_free(IntPtr memblock);
+
 		#endregion
 
 		#region SDL_rwops.h