gnu: Add python-genshi.

gnu: Add python-genshi.

 * gnu/packages/python.scm (python-genshi, python2-genshi): New variables.
 * gnu/packages/patches/python-genshi-add-support-for-python-3.4-AST.patch: New file.
 * gnu/packages/patches/python-genshi-buildable-on-python-2.7.patch: New file.
 * gnu/packages/patches/python-genshi-disable-speedups-on-python-3.3.patch: New file.
 * gnu/packages/patches/python-genshi-fix-tests-on-python-3.5.patch: New file.
 * gnu/packages/patches/python-genshi-isstring-helper.patch: New file.
 * gnu/packages/patches/python-genshi-stripping-of-unsafe-script-tags.patch: New file.
 * gnu/local.mk (dist_patch_DATA): Add them.

Signed-off-by: Arun Isaac <arunisaac@systemreboot.net>