detach keysig generation from pub key export, so that an existing
keysig can be verified later.

key++: normalize id and lc()

allow signing using an alternate secret key, like in pcpdecrypt()

malloc() new pointers in functions only if not NULL, e.g. pcp_gennonce()

check pub key count in pcp.c before calling verify signature, croak if count==0

vault checksum: add keysigs as well

Add newlines to headers in define.h, so strlen() later catches the whole length.

Check is_utf8 license.
  also found in https://gd.meizo.com/_files/lpc/ext/utf8.c

c++ destructor double free mess

Idea from encfs:
       --extpass=program
           Specify an external program to use for getting the user password.  When the external program
           is spawned, the environment variable "RootDir" will be set to contain the path to the root
           directory.  The program should print the password to standard output.

           EncFS takes everything returned from the program to be the password, except for a trailing
           newline (\n) which will be removed.

           For example, specifying --extpass=/usr/lib/ssh/ssh-askpass will cause EncFS to use ssh's
           password prompt program.

           Note: EncFS reads at most 2k of data from the password program, and it removes any trailing
           newline.  Versions before 1.4.x accepted only 64 bytes of text.

       -S, --stdinpass
           Read password from standard input, without prompting.  This may be useful for scripting encfs
           mounts.

           Note that you should make sure the filesystem and mount points exist first.  Otherwise encfs
           will prompt for the filesystem creation options, which may interfere with your script.