backport changes to ciphers(1) man page

Backport of patch:
add ECC strings to ciphers(1), point out difference between DH and ECDH

and backport of other other assorted fixes to this man page

 * Make a clear distinction between DH and ECDH key exchange.
 * Group all key exchange cipher suite identifiers, first DH then ECDH
 * add descriptions for all supported *DH* identifiers
 * add ECDSA authentication descriptions
 * add example showing how to disable all suites that offer no
   authentication or encryption
 * update status of static DH (it's now supported)
 * backport descriptions of AES128, AES256, AESGCM
 * backport descriptions of CAMELLIA128, CAMELLIA256
 * backport listing of standard names for ECC cipher suites
   and TLSv1.2 cipher suites
 * backport description of PSK cipher suites