Currently, if you hit ctrl-c at the standard 'Enter password' prompt,
since it is piped directly to gpg, the entry gets cleared. Trying to
read from that entry results in:

  gpg: [don't know]: 1st length byte missing

This patch fixes this.

Tweaked by Jason A. Donenfeld <Jason@zx2c4.com> to add GNU readline
features by using -e in read.