getrandom.2: Remove getentropy(3) details and defer to new getentropy(3) page

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/getrandom.2

@@ -273,8 +273,8 @@ The special treatment of small values of
 .I buflen
 was designed for compatibility with
 OpenBSD's
-.BR getentropy ()
-system call.
+.BR getentropy (3),
+which is nowadays supported by glibc.
 .PP
 The user of
 .BR getrandom ()
@@ -289,33 +289,6 @@ is not specified and
 is less than or equal to 256,
 a return of fewer bytes than requested should never happen,
 but the careful programmer will check for this anyway!
-.\"
-.SS Emulating OpenBSD's getentropy()
-The
-.BR getentropy ()
-system call in OpenBSD can be emulated using the following
-function:
-
-.in +4n
-.nf
-int
-getentropy(void *buf, size_t buflen)
-{
-    int ret;
-
-    if (buflen > 256)
-        goto failure;
-    ret = getrandom(buf, buflen, 0);
-    if (ret < 0)
-        return ret;
-    if (ret == buflen)
-        return 0;
-failure:
-    errno = EIO;
-    return \-1;
-}
-.fi
-.in
 .SH BUGS
 As of Linux 3.19, the following bug exists:
 .\" FIXME patch proposed https://lkml.org/lkml/2014/11/29/16
@@ -324,6 +297,7 @@ Depending on CPU load,
 .BR getrandom ()
 does not react to interrupts before reading all bytes requested.
 .SH SEE ALSO
+.BR getentropy (3),
 .BR random (4),
 .BR urandom (4),
 .BR random (7),