Xerces Update: datatype XMLGregorianCalendarImpl and DurationImpl

Bring patches from Xerces to the JDK:
XMLGregorianCalendarImpl: 20 revisions, 2 of them had bug ids (XERCESJ-1243 and XERCESJ-1097)
DurationImpl: 10 revisions, 4 of them with bug ids (XERCESJ-1416, XERCESJ-1343, XERCESJ-1107 and XERCESJ-1097)

Complete the above would:
1. bring the two classes up to date
2. bring in the following fixes:
    XERCESJ-1243 Major XMLGregorianCalendarImpl converts offset in minutes incorrectly in getTimeZone
    XERCESJ-1097 Major XMLGregorianCalendarImpl format method generates improperly formatted date string
    XERCESJ-1416 Minor NPE creating (invalid) duration
    XERCESJ-1343 Minor [patch] remove some unused cruft in DurationImpl

3. not complete the following:
    XERCESJ-1107 Minor [PATCH] Cleanup inefficient StringBuffer code

    11 classes were modified in this patch. Only that for DurationImpl would be applied.


Note:
       The JDK classes contain major patches, involving a large amount of changes, one patch for example contained 749 insertions(+), 751 deletions(-). The code therefore is significantly different from the Xerces. Therefore, only relevant changes shall be brought over. When in conflict, keep those in the JDK classes to maintain compatibility.