build: Remove compatibility to GDAL 1 and <2.2

[lbartoletti]

This PR aims to cleanup grass code to remove "dead code" since most modern distribution/packaging have GDAL 3.

Fixes #2645

[wenzeslaus]

I think we had some confusion about the test failures at the in-person meeting, but these are real, although I don't quite see a useful message:

...
Building areas...
0..33..66..100
Attaching islands...
0..33..66..100
-----------------------------------------------------
Finding centroids for OGR layer <all_types>...
ERROR: Unable to import OGR datasource <data/all_types_wgs84.gpkg>
... 

[lbartoletti]

I think we had some confusion about the test failures at the in-person meeting, but these are real, although I don't quite see a useful message:

...
Building areas...
0..33..66..100
Attaching islands...
0..33..66..100
-----------------------------------------------------
Finding centroids for OGR layer <all_types>...
ERROR: Unable to import OGR datasource <data/all_types_wgs84.gpkg>
... 

Was a mistake when I've manually deleted some parts of code in v.in.ogr/main.c. It should be fixed in https://github.com/OSGeo/grass/pull/2995/commits/7d45b62c92d63b2357066ebb6b8f472fb8c8b00b

[wenzeslaus]

Probably an ancient GDAL in our CentOS 7 build is causing the build failure. That was exactly the reason to have CentOS 7 to catch cases for these outdated dependencies. However, perhaps now it the time to finally remove our CentOS 7 build. (It anyway uses conda to get things working, so it is not pure CentOS anyway.)

[neteler]

@lbartoletti would you mind to rebase this PR?

[lbartoletti]

@lbartoletti would you mind to rebase this PR?

done.

[neteler]

@metzm , others: any objections to merge this PR?

[nilason]

@metzm , others: any objections to merge this PR?

I'd welcome this simplification of the code! I noticed some places where calls to GDAL are defined as macros / typedef depending on version. Those may probably be removed all together and be replaced by directly using the GDAL API. I made a comments in-line for the cases which could be relevant for this change.

[metzm]

Very nice, no objections from my side to drop support for those old GDAL versions.

The suggestions of @nilason should be applied before merging. All macros and typedefs related to GDAL versions before 2.2 can go.

[lbartoletti]

Very nice, no objections from my side to drop support for those old GDAL versions.

The suggestions of @nilason should be applied before merging. All macros and typedefs related to GDAL versions before 2.2 can go.

@nilason @metzm It's done in my last commit, and I apologize for my late reaction.

[nilason]

Thanks @lbartoletti ! Looks good to me.

(This removes some 500 lines of obsolete code!)

[wenzeslaus]

This removes some 500 lines of obsolete code!

Thanks! That's really great!

[wenzeslaus]

Issues raised by @nilason and further elaborated on by @metzm were addressed. Compatibility wrappers are removed from the headers which ensures ensures there are not used elsewhere.

There should be no impact on user code even with the change in gis.h if it is already portable code.

I assume these are all occurrences of GDAL_VERSION_NUM in the source code, but even if they are not, they are easy to find and would not harm this great PR.