Starting from DMD2.027 (now that std.c.stdlib plain imports core.stdc.stdlib), a few of useful functions got lost. Namely itoa and ultoa. There might be other functions missing, too, I didn't investigate into it very well.
I'm weary of adding non-standard functions to the plain stdc.stdlib, so I'm closing this.
I appreciate the 'spring cleaning' you are doing now, but some non-standard functions are useful and I'd like to keep them, like alloca() and the GNU (Linux) *_unlocked() functions like fgets_unlocked(). Thank you.