_toupper
========

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/_toupper.html

Gnulib module: ---

Portability problems fixed by Gnulib:

Portability problems not fixed by Gnulib:

  * This function is missing on some platforms: macOS 11.1, Minix 3.1.8, Android 4.4.