Add missing stdio functions to libc

[benni_stuerz.xyz]

Summary

These are some very important libc functions that have been missing.

[getz]

lmao

[obiwac]

I think this is unlikely to land - I suggest you attempt to get this included into POSIX first.

[fuz]

lib/libc/stdio/sgetc.c

6

You wrote this, not the University of California. Put your own name and email in. License text can be omitted if SPDX identifier is used.

38

Needs to account for empty strings.
Also, the strcspn bit doesn't make any sense.

lib/libc/stdio/sgets.c

39–41

lib/libc/stdio/sgetz.c

40

The condition ((j >> 8) & 3) != 5 always holds.

[benni_stuerz.xyz]

Make sgetc(3) more useful.

[benni_stuerz.xyz]

fix declaration of sgetc(3) in stdio.h

[benni_stuerz.xyz]

fuz@ when is this gonna land in POSIX :)