Upgrade the winGRASS-OSGeo4W build environment to a newer GDAL version

• Upgrade the GDAL version by the OSGeo4W installer

See eg. #3716

Source code update for a new major GDAL version

• grass/trunk/mswindows/osgeo4w/package.sh​ - update of the package script
• grass/trunk/lib/raster/gdal.c​ - update of the raster lib

See eg.

• r73839

Example for a GDAL upgrade from 2.3.x to 2.4.x:

Modified: grass/trunk/mswindows/osgeo4w/package.sh
===================================================================
--- grass/trunk/mswindows/osgeo4w/package.sh	2018-12-25 14:38:35 UTC (rev 73832)
+++ grass/trunk/mswindows/osgeo4w/package.sh	2018-12-25 19:58:36 UTC (rev 73833)
@@ -118,7 +118,7 @@
 [ -d mswindows/osgeo4w/lib ] || mkdir mswindows/osgeo4w/lib 
 dll_to_a $OSGEO4W_ROOT_MSYS/bin/proj_5_2.dll    mswindows/osgeo4w/lib/libproj
 dll_to_a $OSGEO4W_ROOT_MSYS/bin/iconv.dll       mswindows/osgeo4w/lib/libiconv
-dll_to_a $OSGEO4W_ROOT_MSYS/bin/gdal203.dll     mswindows/osgeo4w/lib/libgdal
+dll_to_a $OSGEO4W_ROOT_MSYS/bin/gdal204.dll     mswindows/osgeo4w/lib/libgdal
 dll_to_a $OSGEO4W_ROOT_MSYS/bin/liblas_c.dll    mswindows/osgeo4w/lib/liblas_c
 dll_to_a $OSGEO4W_ROOT_MSYS/bin/geos_c.dll      mswindows/osgeo4w/lib/libgeos_c
 dll_to_a $OSGEO4W_ROOT_MSYS/bin/libtiff.dll     mswindows/osgeo4w/lib/libtiff

Modified: grass/trunk/lib/raster/gdal.c
===================================================================
--- grass/trunk/lib/raster/gdal.c	2018-12-25 20:03:33 UTC (rev 73836)
+++ grass/trunk/lib/raster/gdal.c	2018-12-25 20:04:13 UTC (rev 73837)
@@ -115,6 +115,7 @@
 	"libgdal1.7.0.so",
 # endif
 # ifdef _WIN32
+	"gdal204.dll",        
 	"gdal203.dll",        
 	"gdal202.dll",        
 	"gdal201.dll",