Fixed 0003526: Custom field regular expression doesn't prevent invalid bug entry.

M core/custom_field_api.php

• (custom_field_validate): to check the validiting of a custom field value.

M bug_report.php

• Make sure that custom field values are valid before adding the bug.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2308 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9