devscripts: multiple vulnerabilities

CVE-2012-2240: Raphael Geissert discovered that dscverify does not perform sufficient validation and does not properly escape arguments to external commands, allowing a remote attacker (as when dscverify is used by dget) to execute arbitrary code.

CVE-2012-2241: Raphael Geissert discovered that dget allows an attacker to delete arbitrary files when processing a specially-crafted .dsc or .changes file, due to insuficient input validation.

CVE-2012-2242: Raphael Geissert discovered that dget does not properly escape arguments to external commands when processing .dsc and .changes files, allowing an attacker to execute arbitrary code. This issue is limited with the fix for CVE-2012-2241, and had already been fixed in version 2.10.73 due to changes to the code, without considering its security implications.