Backport PR #10793 on branch 5.x

Merge pull request  #10793 from Carreau/wn

Consolidate What's new dev and 5.5

docs/source/whatsnew/index.rst

@@ -20,7 +20,6 b' development work they do here in a user friendly format.'
 .. toctree::
    :maxdepth: 1
 
-   development
    version5
    github-stats-5
    version4

docs/source/whatsnew/version5.rst

@@ -8,6 +8,36 b' IPython 5.4.1'
 Released a few hours after 5.4, fix a crash when
 ``backports.shutil-get-terminal-size`` is not installed. :ghissue:`10629`
 
+IPython 5.5
+===========
+
+System Wide config
+------------------
+
+- IPython now looks for config files in ``{sys.prefix}/etc/ipython``
+  for environment-specific configuration.
+- Startup files can be found in ``/etc/ipython/startup`` or ``{sys.prefix}/etc/ipython/startup``
+  in addition to the profile directory, for system-wide or env-specific startup files.
+
+See :gh:`10644`
+
+ProgressBar
+-----------
+
+
+IPython now has built-in support for progressbars::
+
+    In[1]: from IPython.display import ProgressBar
+    ...  : pb = ProgressBar(100)
+    ...  : pb
+
+    In[2]: pb.progress = 50
+
+    # progress bar in cell 1 updates.
+
+See :gh:`10755`
+
+
 IPython 5.4
 ===========