update docs with descriptions and deprecation

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1079)

doc/crypto/RAND_add.pod

@@ -15,8 +15,10 @@ entropy to the PRNG
 
  int  RAND_status(void);
 
+ #if OPENSSL_API_COMPAT < 0x10100000L
  int  RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
  void RAND_screen(void);
+ #endif
 
 =head1 DESCRIPTION
 
@@ -42,6 +44,8 @@ or L<RAND_load_file(3)>.
 
 RAND_seed() is equivalent to RAND_add() when B<num == entropy>.
 
+RAND_event() and RAND_screen() are deprecated and should not be called.
+
 =head1 RETURN VALUES
 
 RAND_status() returns 1 if the PRNG has been seeded
@@ -53,6 +57,11 @@ RAND_screen calls RAND_poll().
 
 The other functions do not return values.
 
+=head1 HISTORY
+
+RAND_event() and RAND_screen() are deprecated since OpenSSL
+1.1.  Use the functions described above instead.
+
 =head1 SEE ALSO
 
 L<rand(3)>, L<RAND_egd(3)>,