fills left bits with zero, and we have exact 32bit unsigned value
(uint32_t), so there is no reason to add "& 0x7fffffff" here.

MFC after:      1 week

harder.

2) ACM paper require seed to be in [1, 2^31-2] range, so use the same range
shifting as already done for rand(3). Also protect srandomdev() + TYPE_0 case
(non default) from negative seeds.

3) Don't check for valid "type" range in setstate(), it is always valid as
calculated. Instead add a check that rear pointer not exceeed end pointer.

MFC after:      1 week

returning NULL:

"Upon successful completion, initstate() and setstate() shall return a
pointer to the previous state array; otherwise, a null pointer shall
be returned.

Although some implementations of random() have written messages to
standard error, such implementations do not conform to POSIX.1-2008."

2) Move error detections earlier to prevent state modifying.

MFC after:      1 week

NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3,
so follow suit to make comparison easier.

source sysctl(KERN_ARND) and remove the fallback code.

Obtained from:	OpenBSD
Reviewed by:	secteam
MFC after:	1 month

srandomdev(). This doesn't actually work
with any modern C compiler:

In particular, both clang and modern gcc
verisons silently elide any xor operation
with 'junk'.

Approved by:	secteam
MFC after:	3 days

This fixes a race condition where another thread may fork() before CLOEXEC
is set, unintentionally passing the descriptor to the child process.

This commit only adds O_CLOEXEC flags to open() or openat() calls where no
fcntl(fd, F_SETFD, FD_CLOEXEC) follows. The separate fcntl() call still
leaves a race window so it should be fixed later.

Reviewed by:	ache
MFC after:	3 days

clause.

# If I've done so improperly on a file, please let me know.