[CVE-2010-4651] Do not let a malicious patch create files above current directory

[CVE-2010-4651] Do not let a malicious patch create files above current directory

This addresses CVE-2010-4651, reported by Jakub Wilk.
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2010-4651
* src/util.c (strip_leading_slashes): Reject absolute file names
and file names containing a component of "..".
* tests/bad-filenames: New file.  Test for this.
* tests/Makefile.am (TESTS): Add it.
Improvements by Andreas Gruenbacher.

Change-Id: I2f85671214a71c84461b1b2c805c7f48f3b3f922
Signed-off-by: JinWang An <jinwang.an@samsung.com>