Fix[bmqa]: Remove unused Session::impl() function (#519)

This function is not used within the BlazingMQ code, and exposes
publically the PIMPL implementation that is used by `bmqa::Session`.
Because we do not use this function, and because it is part of the
public (documented!) API, users could break our session invariants.
This patch removes this function from the API.  While this is a breaking
change, we do not want any user to be using this function, so we should
be okay with breaking them.

Signed-off-by: Patrick M. Niedzielski <[email protected]>

Author: pniedzielski

src/groups/bmq/bmqa/bmqa_session.h

@@ -1159,13 +1159,6 @@ class Session : public AbstractSession {
     /// been started.
     int configureMessageDumping(const bslstl::StringRef& command)
         BSLS_KEYWORD_OVERRIDE;
-
-    /// Internal
-    ///--------
-
-    /// Do *NOT* use.  Internal function, reserved for BlazingMQ internal
-    /// usage.
-    void* impl();
 };
 
 // ============================================================================
@@ -1181,11 +1174,6 @@ inline int Session::confirmMessage(const Message& message)
     return confirmMessage(message.confirmationCookie());
 }
 
-inline void* Session::impl()
-{
-    return &d_impl;
-}
-
 }  // close package namespace
 }  // close enterprise namespace