Fix for org.apache.fop.fo.pagination.PageProductionException:
Subsequences exhausted in page-sequence-master which occurred where a
sectPr contained a first page header or footer only.
Inherit default header or footer from previous section if this section
doesn't have one, irrespective of whether this section has a first page
header/footer.
Add some license headers.
page-numbering: only specify initial-page-number on fo:page-sequence if
start number is specified in sectPr.
When performing MAILMERGE, honour formatting switches.  Basic
implementation.
getNumberXmlNode. don't insert "?" when triple.getNumString() returns
null
Numbering in PDF output: get hanging indents right.