Mention changes to exit and quit in what's new docs.

docs/source/whatsnew/version0.11.txt

@@ -385,3 +385,7 b' to 0.10.2.'
 * The installation of scripts on Windows was broken without setuptools, so we now
   depend on setuptools on Windows.  We hope to fix setuptools-less installation,
   and then remove the setuptools dependency.
+
+* Capitalised Exit and Quit have been dropped ways to exit IPython. The lowercase forms
+  of both work either as a bare name (``exit``) or a function call (``exit()``).
+  You can assign these to other names using exec_lines in the config file.