pngdriver, cairodriver: debug msg added

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@62716 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/cairodriver/graph.c

@@ -124,6 +124,7 @@ static void init_file(void)
     p = getenv("GRASS_RENDER_FILE");
     if (!p || strlen(p) == 0)
 	p = DEFAULT_FILE_NAME;
+    G_debug(1, "cairo: GRASS_RENDER_FILE: %s", p);
 
     ca.file_name = p;
 

lib/pngdriver/graph_set.c

@@ -91,6 +91,7 @@ int PNG_Graph_set(void)
     p = getenv("GRASS_RENDER_FILE");
     if (!p || strlen(p) == 0)
 	p = FILE_NAME;
+    G_debug(1, "png: GRASS_RENDER_FILE: %s", p);
 
     png.file_name = p;