Fixed 0003266: Possible patches against CVS (Not all changes were applied, see bug for details)
Fixed 0003292: Exporting csv results in "cannot modify header" error.

M csv_export.php

• Some echos were executed before the header()'s.

M proj_doc_add_page.php

• Marking the document field as required.
• Removed the max size hidden field (not used)

M core/error_api.php

• Add a check before calling ob_end_clean() in order to avoid a notice.
• Some fixes/enhancements to dumping of the stack trace.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2229 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9