Updated event_listener.rst

Updated event_listener.rst to use the new KernelEvent::isMasterRequest method
Added Versionadded directive to event_listener.rst

Added missing Versionadded directive to event_listener.rst
Added KernelEvent::isMasterRequest method reference
Fixed internals.rst syntax
feature #3776 Updated event_listener.rst (bfgasparin)

This PR was merged into the 2.4 branch.

Discussion
----------

Updated event_listener.rst

Updated event_listener.rst to use the new KernelEvent::isMasterRequest method

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4+
| Fixed tickets | none

Commits
-------

4fc3b6a Fixed internals.rst syntax
a6b17a0 Added KernelEvent::isMasterRequest method reference
8e8b8a0 Added Versionadded directive to event_listener.rst
0127bd2 Updated event_listener.rst