[Proj] Datum shift to WGS84 for Dutch coordinate system (EPSG:28992)

[Jan Hartmann]

For all the fans of the official Dutch coordinate system ("Amersfoort", 
"Rijksdriehoeksnet", "RD"), EPSG:28992, I finally figured out what the 
right codes are in our beloved epsg database, version 4.9, 24 nov 2009. 
See text and attached Excel spreadsheet at:

http://trac.osgeo.org/geotiff/ticket/22#comment:3

Comments are appreciated and I'll let you know when the earth changes 
form again.

Jan