Fix compile errors for 64-bits windows

pandatool/src/maxegg/maxEgg.cxx

@@ -303,7 +303,7 @@ IObjParam *MaxEggPlugin::iObjParams;
    dialog box that appears at the beginning of the conversion process.
  */
 
-BOOL CALLBACK MaxEggPluginOptionsDlgProc( HWND hWnd, UINT message, 
+INT_PTR CALLBACK MaxEggPluginOptionsDlgProc( HWND hWnd, UINT message, 
                                           WPARAM wParam, LPARAM lParam ) 
 {
   MaxOptionsDialog *tempEgg;

pandatool/src/maxegg/maxOptionsDialog.cxx

@@ -241,7 +241,7 @@ MaxEggOptions::MaxEggOptions() {
     _successful = false;
 }
 
-BOOL CALLBACK MaxOptionsDialogProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam ) 
+INT_PTR CALLBACK MaxOptionsDialogProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam ) 
 {
     char tempFilename[2048];
     //We pass in our plugin through the lParam variable. Let's convert it back.

pandatool/src/maxegg/maxOptionsDialog.h

@@ -41,7 +41,7 @@ char *ChunkLoadString(ILoad *iload, char *buffer, int maxBytes);
 int ChunkLoadInt(ILoad *iload);
 bool ChunkLoadBool(ILoad *iload);
 void SetICustEdit(HWND wnd, int nIDDlgItem, char *text);
-BOOL CALLBACK MaxOptionsDialogProc( HWND hWnd, UINT message, 
+INT_PTR CALLBACK MaxOptionsDialogProc( HWND hWnd, UINT message, 
                                     WPARAM wParam, LPARAM lParam );
 
 struct MaxEggOptions

pandatool/src/maxprogs/maxEggImport.cxx

@@ -124,7 +124,7 @@ unsigned int MaxEggImporter::Version()
   return 100;
 }
 
-static BOOL CALLBACK AboutBoxDlgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
+static INT_PTR CALLBACK AboutBoxDlgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
   switch (msg) {
   case WM_INITDIALOG:
@@ -150,7 +150,7 @@ void MaxEggImporter::ShowAbout(HWND hWnd)
 }
 
 
-static BOOL CALLBACK ImportDlgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
+static INT_PTR CALLBACK ImportDlgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
   MaxEggImporter *imp = (MaxEggImporter*)GetWindowLong(hWnd,GWL_USERDATA); 
   switch (msg) {