KEYDB_SEARCH_DESC - no point in reinventing the wheel. This allows the
helper program to search the keyserver by fingerprint if desired (and the
keyserver supports it). Note that automatic fingerprint promotion during
refresh only applies to v4 keys as a v4 fingerprint can be easily changed
into a long or short key id, and a v3 cannot.
Take two copies of hextobyte() from pubkey-enc.c and getkey.c and make
them into one copy in misc.c.