mark perl test scripts executable

These scripts are not run directly as part of a normal build, so no
one noticed that they did not have the +x bit.  Mark them executable
to make it more obvious that they can be run directly (when debugging,
for example).

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jrn