According to earlier standards, usage of select(), FD_CLR, FD_ISSET, FD_SET and FD_ZERO
just need include headers: sys/time.h, sys/types.h and unistd.h. So include sys/select.h
in time.h to compatible with it. Or mbedtls library would build break in calling select()
and FD_* related functions.
https://pubs.opengroup.org/onlinepubs/007908799/xsh/select.html