[openssl/openssl] 425e97: Add some documentation for X509_gmtime_adj()

[Matt Caswell]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 425e972dfaf867affb5b3d438d9ca67bb6aeed65
      https://github.com/openssl/openssl/commit/425e972dfaf867affb5b3d438d9ca67bb6aeed65
  Author: Matt Caswell <matt at openssl.org>
  Date:   2022-08-18 (Thu, 18 Aug 2022)

  Changed paths:
    M doc/man3/X509_cmp_time.pod
    M util/missingcrypto.txt

  Log Message:
  -----------
  Add some documentation for X509_gmtime_adj()

Other very similar functions were documented, but this one was missing.

Reviewed-by: Hugo Landau <hlandau at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18974)