gpg: Allow predefined names as answer to the keygen.algo prompt.
* g10/keygen.c (ask_algo): Add list of strings.
(backported from commit b1d5ed6ac842469afcb84868d0f6641dc286a6c7)
[dkg: rebased to STABLE-BRANCH-1-4]
- Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>