Make File Dialog case insensitive

Change FileDialog and EditorFileDialog to use case insensitive string
comparisons when saving files to avoid duplicate file extensions.

editor/gui/editor_file_dialog.cpp

@@ -127,7 +127,7 @@ void EditorFileDialog::_native_dialog_cb(bool p_ok, const Vector<String> &p_file
 				int filter_slice_count = flt.get_slice_count(",");
 				for (int j = 0; j < filter_slice_count; j++) {
 					String str = (flt.get_slice(",", j).strip_edges());
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}
@@ -565,7 +565,7 @@ void EditorFileDialog::_action_pressed() {
 				String flt = filters[i].get_slice(";", 0);
 				for (int j = 0; j < flt.get_slice_count(","); j++) {
 					String str = flt.get_slice(",", j).strip_edges();
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}
@@ -584,7 +584,7 @@ void EditorFileDialog::_action_pressed() {
 				int filterSliceCount = flt.get_slice_count(",");
 				for (int j = 0; j < filterSliceCount; j++) {
 					String str = (flt.get_slice(",", j).strip_edges());
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}

scene/gui/file_dialog.cpp

@@ -138,7 +138,7 @@ void FileDialog::_native_dialog_cb(bool p_ok, const Vector<String> &p_files, int
 				int filter_slice_count = flt.get_slice_count(",");
 				for (int j = 0; j < filter_slice_count; j++) {
 					String str = (flt.get_slice(",", j).strip_edges());
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}
@@ -473,7 +473,7 @@ void FileDialog::_action_pressed() {
 				String flt = filters[i].get_slice(";", 0);
 				for (int j = 0; j < flt.get_slice_count(","); j++) {
 					String str = flt.get_slice(",", j).strip_edges();
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}
@@ -492,7 +492,7 @@ void FileDialog::_action_pressed() {
 				int filterSliceCount = flt.get_slice_count(",");
 				for (int j = 0; j < filterSliceCount; j++) {
 					String str = (flt.get_slice(",", j).strip_edges());
-					if (f.match(str)) {
+					if (f.matchn(str)) {
 						valid = true;
 						break;
 					}