filter-transform: Migration code for earlier stable versions

This fixes #116 which was caused by a refactor in commit efb6b0b. This bug was left undiscovered until users started upgrading from the last stable version to the current pre-release.

source/filters/filter-transform.cpp

@@ -115,9 +115,23 @@ transform::transform_instance::~transform_instance()
 
 void transform::transform_instance::load(obs_data_t* settings)
 {
+	migrate_settings(settings);
 	update(settings);
 }
 
+inline void migrate_settings(obs_data_t* settings)
+{
+	uint64_t version = static_cast<uint64_t>(obs_data_get_int(settings, S_VERSION));
+
+	switch (version & STREAMFX_MASK_COMPAT) {
+	case 0:
+		obs_data_set_double(settings, ST_ROTATION_X, -obs_data_get_double(settings, ST_ROTATION_X));
+		obs_data_set_double(settings, ST_ROTATION_Y, -obs_data_get_double(settings, ST_ROTATION_Y));
+	}
+
+	obs_data_set_int(settings, S_VERSION, STREAMFX_VERSION);
+}
+
 void transform::transform_instance::update(obs_data_t* settings)
 {
 	// Camera