Add missing @since to docstrings of some new methods

panda/src/display/displayRegion.I

@@ -160,6 +160,8 @@ set_dimensions(const LVecBase4 &dimensions) {
  * Changes the range of the depth buffer this DisplayRegion writes to.
  * The parameters range from 0 to 1.  It is legal for the near value to be
  * larger than the far value.
+ *
+ * @since 1.11.0
  */
 INLINE void DisplayRegion::
 set_depth_range(PN_stdfloat near_depth, PN_stdfloat far_depth) {

panda/src/event/asyncTaskManager.I

@@ -36,6 +36,8 @@ get_clock() {
 /**
  * Adds a new task which calls the indicated function to the task manager.
  * Returns the newly created FunctionAsyncTask object.
+ *
+ * @since 1.11.0
  */
 INLINE AsyncTask *AsyncTaskManager::
 add(const std::string &name, FunctionAsyncTask::TaskFunction function) {

panda/src/pgraph/depthBiasAttrib.h

@@ -37,6 +37,8 @@ class FactoryParams;
  * with a value of 1 beneath another DepthBiasAttrib with a value of 2
  * presents a net offset of 3.  (A DepthBiasAttrib will not, however,
  * combine with any other DepthBiasAttribs with a lower override parameter.)
+ *
+ * @since 1.11.0
  */
 class EXPCL_PANDA_PGRAPH DepthBiasAttrib : public RenderAttrib {
 private: