[openssl/openssl] 405d6d: Add some documentation for X509_gmtime_adj()

[Matt Caswell]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: 405d6dcd09388d34cad8290601dd726d9484f6c0
      https://github.com/openssl/openssl/commit/405d6dcd09388d34cad8290601dd726d9484f6c0
  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)

(cherry picked from commit 425e972dfaf867affb5b3d438d9ca67bb6aeed65)