Return type of getrandom(2)

The manual page says the return type of getrandom(2) is int, but
ssize_t would be more natural (see read(2) for comparison).  The
kernel uses ssize_t internally, which is converted to long on the
system call boundary.

The difference does not currently matter because the return value is
limited to much less than INT_MAX in the implementation.

Should we use int or ssize_t in the glibc system call wrapper?