[PROJ] Use of EPSG codes in proj_create()

[Oliver Eichler]

Hi,

I am working on the transition of QMapShack from version 4 to version 5 
API. So far so good. There is only on thing that breaks. The use of EPSG 
codes for projection strings.

That's what I try to do:

     // used PROJ version: 6.0.0
     // PJ * pj = proj_create(PJ_DEFAULT_CTX, "EPSG:3395");      // [1] 
result for x and y is inf
     PJ * pj = proj_create(PJ_DEFAULT_CTX, "+proj=merc");        // [2] 
result is expected one
     // PJ * pj = proj_create(PJ_DEFAULT_CTX, "+init=EPSG:3395") // [3] 
pj is nullptr
     PJ_COORD pt = {11 * DEG_TO_RAD, 48 * DEG_TO_RAD};
     size_t s = proj_trans_generic(pj, PJ_FWD,
                                 &pt.xy.x, 0, 1,
                                 &pt.xy.y, 0, 1,
                                 0,0,0,
                                 0,0,0);


If I use [1] to create a PJ object I succeed with a pointer. However if 
I use it in proj_trans_generic() the result for x and y ins INF.

Version [2] is fine and works as expected.

Version [3] fails to create a PJ object, but as far as I understand the 
docs this is perfectly fine.

So how is this intended to work? Maybe a bit of background about this: 
QMapShack addresses consumers not scientific users. The experience of 
the last years revealed that it is much easier to tell a user to use an 
EPSG code as projection rather than a lengthy "+proj=..." string with 
all kinds of possibilities to introduce typos. That's why I would like 
to keep the possibility to use EPSSG codes.


Thanks for feedback

Oliver