trunk: Remove error introduced in r87 of branches/5.0, ported in r88:

In row_ins_set_detailed(), truncate the tmpfile by os_file_set_eof(), because
trx_set_detailed_error_from_file() does not call ftell() to determine
the actual length of the file.  This bug resulted in trash being appended
to foreign key error messages.

row/row0ins.c

@@ -591,10 +591,16 @@ row_ins_set_detailed(
 	mutex_enter(&srv_misc_tmpfile_mutex);
 	rewind(srv_misc_tmpfile);
 
-	ut_print_name(srv_misc_tmpfile, trx, foreign->foreign_table_name);
-	dict_print_info_on_foreign_key_in_create_format(srv_misc_tmpfile,
+	if (os_file_set_eof(srv_misc_tmpfile)) {
+		ut_print_name(srv_misc_tmpfile, trx,
+				foreign->foreign_table_name);
+		dict_print_info_on_foreign_key_in_create_format(
+				srv_misc_tmpfile,
 				trx, foreign, FALSE);
 		trx_set_detailed_error_from_file(trx, srv_misc_tmpfile);
+	} else {
+		trx_set_detailed_error(trx, "temp file operation failed");
+	}
 
 	mutex_exit(&srv_misc_tmpfile_mutex);
 }