implicit function declaration in imlib.c (macOS linux VM)

[JeffreyDeanBrown]

When compiling feh v3.10.3 on a VM of slackware aarch64 version 15.0+ (using apple virtualization), the compiler errors with an implicit function declaration for the mkstemps() call on line 884 of imlib.c .

I think it's because is not included in imlib.c and mkstems() is not POSIX standard.