general: Fix assorted compiler warnings

pandatool/src/gtk-stats/gtkStatsChartMenu.cxx

@@ -161,7 +161,7 @@ do_update() {
   _last_level_index = view.get_level_index();
 
   const PStatClientData *client_data = _monitor->get_client_data();
-  if (client_data->get_num_collectors() > _collector_items.size()) {
+  if ((size_t)client_data->get_num_collectors() > _collector_items.size()) {
     _collector_items.resize(client_data->get_num_collectors(), std::make_pair(nullptr, nullptr));
   }
 

pandatool/src/palettizer/txaLine.cxx

@@ -357,6 +357,7 @@ match_egg(EggFile *egg_file) const {
     case KW_linear:
     case KW_mipmap:
     case KW_anisotropic:
+    case KW_srgb:
       // These mean nothing to an egg file.
       break;
 

pandatool/src/pstatserver/pStatThreadData.cxx

@@ -235,7 +235,7 @@ get_frame_number_after(double time, int start_at) const {
 
   while (end < time) {
     ++i;
-    if (i >= _frames.size()) {
+    if ((size_t)i >= _frames.size()) {
       break;
     }
     if (_frames[i] != nullptr) {