Improve access to SAX locator object
Improve access to SAX locator object

Link the SAX state to the handler, and allow the handler to obtain the
current location at points other than entry to an element.  Prototype
association of location with character information (aka "text").

jonfoster/pyxb-upstream-mirror,pabigot/pyxb,balanced/PyXB,jonfoster/pyxb-upstream-mirror,CantemoInternal/pyxb,jonfoster/pyxb2,jonfoster/pyxb2,balanced/PyXB,jonfoster/pyxb2,CantemoInternal/pyxb,jonfoster/pyxb-upstream-mirror,balanced/PyXB,pabigot/pyxb,CantemoInternal/pyxb