eliminate unnecessary use of strlen() (on a string constant)

We can use the same trick used in handy.h:

>    /* concatenating with "" ensures that only literal strings are accepted as argument */
>    #define STR_WITH_LEN(s)  ("" s ""), (sizeof(s)-1)
>
>    /* note that STR_WITH_LEN() can't be used as argument to macros or functions that
>     * under some configurations might be macros, which means that it requires the full
>     * Perl_xxx(aTHX_ ...) form for any API calls where it's used.
>     */

We dont use STR_WITH_LEN() because we need to use it in a macro, so
we just unroll it where we need it.
don't accidentally include .gdb_history in any distributions