[GRASS5] Reversed Krovak projection implemented (new Kavork)

[Markus Neteler]

Hi again,

Jaro Hofierka and me have now implemented both Krovak and reversed
Krovak, called "Kavork" (read backwards), projections into GRASS (see
also my previous mail). The Kavork projection exists in parallel to Krovak.
Most Czech/Slovak GIS users will need Kavork rather than Krovak - Kavork is
Krovak with switched coordinate axes.

The new PJ_kavork.c should also go into the original PROJ4 (PJ_krovak.c
is already present in latest PROJ4) along with the added "Hermannskogel"
datum.

Validation:

Radim and me have used v.proj to transform Czech S42 projected vector maps
(Datum Pulkovo, Krassovsky ellips, tmerc prj) to Kavork projection datum
Hermannskogel, Bessel ellips, conic proj). The error was around 40m in
North-South direction and 15m in East-West direction - I assume due to the
missing datum transformation. Apart from the shift error the both maps (the
transformed S42 map and a reference map generated by Czech data provider in
Kavork) match well.

If there is interest, I can upload the additional Krovak and Kavork to
CVS/head.

Cheers

 Markus