[gtk-doc] make: ignore pycache dirs

[Stefan Sauer <stefkost src gnome org>]

commit 1736e2d1d570d97cefcc42904055cda6d6443360
Author: Stefan Sauer <ensonic users sf net>
Date:   Fri Jun 2 09:03:58 2017 +0200

    make: ignore pycache dirs

 Makefile.am |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 405e4ab..f351a5e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -125,7 +125,8 @@ MAINTAINERCLEANFILES = \
        RELNOTES.txt \
        ChangeLog-?.?? \
        gtk-doc-*.tar.xz \
-       build-aux
+       build-aux \
+       gtkdoc/__pycache__ tests/__pycache__
 
 -include $(top_srcdir)/git.mk