The Assuan protocol is now used for socket communication. This

The Assuan protocol is now used for socket communication. This
requires libassuan and libgpg-error. Of course this will affect error
reporting and error codes. The errors returned are error codes used by
libgpg-error. They are the GPG_ERR_USER_N codes when no standard GPG
error will do (non-key and syntax related errors).

Some protocol commands have also changed:

    HELP  - has been removed

    CACHE - It's subcommands CLEARCACHE, CACHETIMEOUT and ISCACHED
	    have been made into their own protocol commands. The CACHE
	    command itself and RESETCACHE (also the
	    cache_reset_timeout configuration parameter) have been
	    removed.

    STORE - First the client sends just the STORE command by itself,
	    then after a INQUIRE server response the client sends:

	    D <element path>

	    This is part of the Assuan protocol so a client can send
	    more than 1000 bytes (the maximum protocol command line
	    length).

    OPEN  - A client can open another file without reconnecting to the
	    server. If the OPEN of the new file fails, then no file
	    will be open at all. Also, when a key is specified when
	    opening a new (non-existant) file, both the file and key
	    will be stored in the cache. Before you had to SAVE before
	    the key was added.

Some bugfixes that I should have cherry-picked to avoid a large commit
but got carried away:

All non-cache related commands will check if the file has been
modified before continueing.

Fixed a double free() in the LIST command.

Zero out the shared memory on exit.

Don't unlink() a socket or other file that wasn't created by pwmd.

Zero out the temporary file_cache_t variables after use.o

When a file was known not to be cached because of an empty key but
still had a slot used for the same file, a new slot was being used.
Fixed.

Added debianization stuff.