doc: Document !768

doc/changes/ipc/mr.721.md

@@ -1,5 +1,6 @@
 ---
 - mr.754
+- mr.768
 ---
 Now that there is a interface that allows the compositor to support
 multi-client rendering use that instead of doing our own rendering.

doc/changes/ipc/mr.768.md

@@ -0,0 +1,2 @@
+Ensure that functions that require the compositor can't be called if a session
+has not been created yet.

doc/changes/xrt/mr.705.2.md

@@ -1,2 +1,5 @@
+---
+- mr.768
+---
 xrt: Add XRT_ERROR_EGL_CONFIG_MISSING error, to handle missing config from
 EGL compositor creation call.

doc/changes/xrt/mr.768.md

@@ -0,0 +1,2 @@
+Add new IPC session not created error `XRT_ERROR_IPC_SESSION_NOT_CREATED`, as
+some functions can not be called without first creating a session.