[Proj] Implementation(s) for Oblique Stereographic

[Oscar van Vlijmen]

When sorting out the stereographic problems of some applications and
databases, one might also want to look at the oldies:

2036: NAD_1983_CSRS98_New_Brunswick_Stereographic
2200: ATS_1977_New_Brunswick_Stereographic
2290: Prince_Edward_Island_Stereographic
2291: NAD_1983_CSRS98_Prince_Edward_Island
22700: Deir_ez_Zor_Levant_Zone
22780: Deir_ez_Zor_Levant_Stereographic

For the above mentioned e.g. the ESRI-ArcGIS projected coordinate systems
list says "Double_Stereographic".

Dutch RD, Romanian Stereo 33 & 70, Polish quasi-stereographic have already
been discussed.
I believe Dutch RD can be approximated with sub-mm accuracy by sterea.
Polish quasi-stereographic can only be approximated by sterea with sub-cm
accuracy. Probably this projection will be in use until at least 2009.
The sterea approximation for Romanian Stereo 70 is also not better than
sub-cm level, but I have not enough test points to verify this.

Collector's item:
the "Alaska Conformal" projection is a unique modified oblique stereographic
projection. See PJ23Z0 or alconfor/inv in GCTP2. The GCTP test suite has
enough test points.