XML import fails due to invalid characters

Our JIRA users have somehow entered 0x1c-characters (file separator) to description-field on a couple of issues. When the database is exported to XML and imported back, the import fails due to the 0x1c character in a CDATA block. It can't even be fixed by changing the description using JIRA, as the invalid character is also in the change history. We had to remove these by hand from the database.

Marked this issue critical as it also breaks upgrading from 3.0.1 to 3.0.3 which relies on export/import.