Work around API changes in python.

Rather than disabling matplotlib, define the missing typedef when
python is older than 2.6.

Note: Matplotlib still isn't supported on these
versions, this change just allows the module to build. A runtime check
will still fail when importing matplotlib.

Change-Id: Id5cd18cf9ea07e115104cecc16b7d1c83c46d6f1
Merge topic 'MPL-buildFix' into master

c0b56815 Work around API changes in python.