* mlibc/include/mlibc.h (_atoi): Declare.
* mlibc/include/ctype.h (isxdigit): Declare.
* mlibc/libc-gcc.c (isxdigit, _atoi): New function.
(atoi): Use it.
* mlibc/libc-mes.c (isxdigit, _atoi): New function.
(atoi): Use it.
* scaffold/tests/7j-strtoull.c (test): Test it.
* make.scm (add-scaffold-test): Build it.