tool/check_patch.py: use temporary dir for temporary files

I personally dislike having my source tree being populated with
untracked files. This uses a temporary dir instead, telling the
user where he/she may find those files.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
tools/run_pylint.py: prevent creation of empty pylintrc

I observed no change in behaviour whether the file exists or not.
Tested with latest upstream pylint.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
tools/check_patch.py: try to keep column count <= 79

This is cosmetic only, but recomended by PEP8 and very much needed
for emacs users.

Signed-off-by: Cleber Rosa <crosa@redhat.com>