Patch to support GRASS 7.2

[Bas Couwenberg]

The libgdal-grass Debian package uses a patch to set the RPATH to the GRASS library directory which is no in the standard library search path.

Some GRASS 7.2 libraries require new libraries (libgrass_btree2 & libgrass_ccmath) which are not linked by the GDAL GRASS plugin and can therefor not be found resulting in errors like these:

$ gdalinfo --version
ERROR 1: libgrass_btree2.7.2.0.so: cannot open shared object file: No such file or directory
ERROR 1: libgrass_btree2.7.2.0.so: cannot open shared object file: No such file or directory
ERROR 1: libgrass_btree2.7.2.0.so: cannot open shared object file: No such file or directory
ERROR 1: libgrass_btree2.7.2.0.so: cannot open shared object file: No such file or directory
GDAL 2.1.2, released 2016/10/24

The attached patch links the new libraries when GRASS 7.2 is detected to resolve those errors.

[Even Rouault]

In 37160:

frmts/grass/pkg/configure: add support for GRASS 7.2 (patch by Bas Couwenberg, fixes #6785)

[Even Rouault]

In 37161:

frmts/grass/pkg/configure: add support for GRASS 7.2 (patch by Bas Couwenberg, fixes #6785)