Merge branch 'refs/heads/t/crypt'

A couple of simple patches which clean up the openssl and gcrypt crypto
backends. The non-trivial parts are the get_public_key() unification,
the memory leak fixes for openssl and the activation of the secmem
pool for gcrypt.

* refs/heads/t/crypt:
  gcrypt: Allocate a secmem pool at startup.
  crypt: Introduce crypt_shutdown().
  crypt: Rename init_random_seed_or_die() -> crypt_init().
  gcrypt: Use ROUND_DOWN() macro.
  crypt: Rename RSA functions.
  crypt: Deduplicate get_public_key().
  crypt.h: Remove two unused constants.
  Rename crypt.c -> openssl.c.

diff --cc NEWS.md
index 9ced85e9019eea7c93c0a4c37f8c632464e2dd58,d0bd6585a3a2f04be5ec262d580bfb8800733498..11f275da582470d97d442d07f9abf6c8a10ff097
--- 1/NEWS.md
--- 2/NEWS.md
+++ b/NEWS.md
@@@ -1,15 -1,6 +1,15 @@@
  NEWS
  ====
  
- the geometry of the terminal changes.
- 
 +-------------------------------------------
 +0.6.2 (to be accounced) "elastic diversity"
 +-------------------------------------------
 +
 +- para_gui no longer waits up to one second to update the screen when
++  the geometry of the terminal changes.
 +- Minor documentation improvements.
++- Improvements to the crypto subsystem.
 +
  ----------------------------------------
  0.6.1 (2017-09-23) "segmented iteration"
  ----------------------------------------

diff --cc client_common.c
Simple merge

diff --cc command.c
Simple merge

diff --cc server.c
Simple merge