libgis: add read/write functions for WKT and srid (#976)

GRASS native projection information is reaching its limits in representing CRS's, while PROJ and GDAL have been substantially enhanced.Use WKT or authority code if possible to convert to different formats

+ libgis: read/write functions for WKT and spatial reference id as recognized by PROJ

+ g.proj: use WKT or authority code if possible

general/g.proj/create.c

@@ -10,8 +10,8 @@ void create_location(const char *location)
 {
     int ret;
 
-    ret = G_make_location_epsg(location, &cellhd, projinfo, projunits,
-                               projepsg);
+    ret = G_make_location_crs(location, &cellhd, projinfo, projunits,
+                               projepsg, projwkt, projsrid);
     if (ret == 0)
 	G_message(_("Location <%s> created"), location);
     else if (ret == -1)
@@ -59,6 +59,14 @@ void modify_projinfo()
 	G_write_key_value_file(path, projepsg);
     }
 
+    if (projwkt != NULL) {
+	G_write_projwkt(NULL, projwkt);
+    }
+
+    if (projsrid != NULL) {
+	G_write_projsrid(NULL, projsrid);
+    }
+
     if ((old_cellhd.zone != cellhd.zone) ||
 	(old_cellhd.proj != cellhd.proj)) {
 	/* Recreate the default, and current window files if projection