.gitattributes: introduce git attributes for improved Python diffs

In the absence of respective instructions, git will use a rather generic
approach to generate diffs and patches. Introduce a git attributes file
which results in improved output for Python sources (i.e. all protocol
decoders).

Signed-off-by: Gerhard Sittig <gerhard.sittig@gmx.net>

Author: gsigh

.gitattributes

@@ -0,0 +1 @@
+*.py	diff=python