gpg: Add support for Subkey-Expire-Date.
* g10/keygen.c (enum para_name): Add pSUBKEYEXPIREDATE. (proc_parameter_file): Add support for pSUBKEYEXPIREDATE. (read_parameter_file): Add "Subkey-Expire-Date".
Cherry-pick from master commit of:
23bcb78d279ebc81ec9340356401d19cf89985f1
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>