Altered keyfile.c to use the new spawning module

In particular, changed the default printcmd not to "single quote paths
on Win32 for g_spawn_command_line_async", but use the native double
quotes. Also fixed it not to g_strconcat(NULL, ...) if lpr is missing
under Unix. It works, but glib says the first string must not be NULL,
and the command becomes wrong anyway.

src/keyfile.c

@@ -941,19 +941,20 @@ static void load_dialog_prefs(GKeyFile *config)
 
 	/* printing */
 	tmp_string2 = g_find_program_in_path(GEANY_DEFAULT_TOOLS_PRINTCMD);
-#ifdef G_OS_WIN32
+
 	if (!EMPTY(tmp_string2))
 	{
-		/* single quote paths on Win32 for g_spawn_command_line_async */
-		tmp_string = g_strconcat("'", tmp_string2, "' '%f'", NULL);
+	#ifdef G_OS_WIN32
+		tmp_string = g_strconcat(GEANY_DEFAULT_TOOLS_PRINTCMD, " \"%f\"", NULL);
+	#else
+		tmp_string = g_strconcat(GEANY_DEFAULT_TOOLS_PRINTCMD, " %f", NULL);
+	#endif
 	}
 	else
 	{
 		tmp_string = g_strdup("");
 	}
-#else
-	tmp_string = g_strconcat(tmp_string2, " %f", NULL);
-#endif
+
 	printing_prefs.external_print_cmd = utils_get_setting_string(config, "printing", "print_cmd", tmp_string);
 	g_free(tmp_string);
 	g_free(tmp_string2);