Fixed autoconf install regarding ofstd variadic.

Added the location ofstd/variadic to the autoconf install configuration.
Attribute (0040,4005) has not been retired.

Fixed an issue with Scheduled Procedure Step Start DateTime (0040,4005) being
retired accidentally by the 2013 edition of the DICOM standard. The editor
of the DICOM standard, David Clunie, confirmed that this was not intended.
Fixed wrong term "Device Driving Level".

Replaced wrong term "Device Driving Level" by "Digital Driving Level" (DDL).