Bug 707449: Fall back to "usecmap" declaration for embedded CMaps.

CMap objects in PDF _must_ also set the UseCMap dictionary entry,
but in case they violate the spec by not doing so we can still
try to respect the "usecmap" directive in embedded cmap streams.

source/pdf/pdf-cmap-load.c

@@ -72,6 +72,20 @@ pdf_load_embedded_cmap_imp(fz_context *ctx, pdf_document *doc, pdf_obj *stmobj,
 			usecmap = pdf_load_embedded_cmap_imp(ctx, doc, obj, &cycle);
 			pdf_set_usecmap(ctx, cmap, usecmap);
 		}
+		else if (strlen(cmap->usecmap_name) > 0)
+		{
+			fz_try(ctx)
+			{
+				usecmap = pdf_load_system_cmap(ctx, cmap->usecmap_name);
+				pdf_set_usecmap(ctx, cmap, usecmap);
+			}
+			fz_catch(ctx)
+			{
+				fz_rethrow_if(ctx, FZ_ERROR_SYSTEM);
+				fz_report_error(ctx);
+				fz_warn(ctx, "cannot load system CMap: %s", pdf_to_name(ctx, obj));
+			}
+		}
 
 		pdf_store_item(ctx, stmobj, cmap, pdf_cmap_size(ctx, cmap));
 	}