configure: Add spaces after <<EOF heredoc markers for clarity

I mean, they confuse the vim bash syntax highlighter
configure: Let the user enable both built-in protocols and purple

There's no real risk in enabling these, since protocols/purple/purple.c
already avoids adding duplicate protocols in purple_initmodule():

    /* If we already have this one (as a native module), don't
       add a libpurple duplicate. */
    if( find_protocol( prot->info->id ) )
        continue;
doc/bitlbee.xinetd: Move -I to server_args
Fix version in pkg-config file, also change bzr version format slightly

Old bzr version format: bzr-1234
New bzr version format: 3.2.1-bzr-1234

Version spoofing with the BITLBEE_VERSION also changed slightly - it
does not need quotes around the version number anymore for it to compile
correctly.
Fix double slashes in systemd unit templates