update to 1.5.1 (#1276806)

Further fixes/changes:
- Add missing requires of dvipng to python3-matplotlib (#1270202)
- use bundled agg (#1276806)
- Drop cxx patch (was dropped upstream)
- Regenerate search path patch2

20_matplotlibrc_path_search_fix.patch

@@ -1,14 +1,9 @@
-Description: Fixes the path to search for matplotlibrc file
-Forwarded: not-needed
-Author: Sandro Tosi <morph@debian.org>
-
---- a/lib/matplotlib/__init__.py
-+++ b/lib/matplotlib/__init__.py
-@@ -658,10 +658,12 @@ def _get_data_path():
-             raise RuntimeError('Path in environment MATPLOTLIBDATA not a directory')
-         return path
+--- a/lib/matplotlib/__init__.py	2016-04-04 12:54:26.427194940 +0200
++++ b/lib/matplotlib/__init__.py	2016-04-04 12:56:12.662590255 +0200
+@@ -682,9 +682,12 @@
  
--    path = os.sep.join([os.path.dirname(__file__), 'mpl-data'])
+     _file = _decode_filesystem_path(__file__)
+     path = os.sep.join([os.path.dirname(_file), 'mpl-data'])
 +    path = '/usr/share/matplotlib/mpl-data'
      if os.path.isdir(path):
          return path
@@ -18,7 +13,7 @@ Author: Sandro Tosi <morph@debian.org>
      # setuptools' namespace_packages may highjack this init file
      # so need to try something known to be in matplotlib, not basemap
      import matplotlib.afm
-@@ -786,7 +788,7 @@ def matplotlib_fname():
+@@ -812,7 +815,7 @@
                      home, '.matplotlib', 'matplotlibrc')
              return fname