vendor: Add github.com/cznic/lldb and friends (new recursive dependency)

vendor/github.com/cznic/lldb/2pc_docs.go

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+// Copyright 2014 The lldb Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+
+Anatomy of a WAL file
+
+WAL file
+	A sequence of packets
+
+WAL packet, parts in slice notation
+	[0:4],   4 bytes:        N uint32        // network byte order
+	[4:4+N], N bytes:        payload []byte  // gb encoded scalars
+
+Packets, including the 4 byte 'size' prefix, MUST BE padded to size == 0 (mod
+16). The values of the padding bytes MUST BE zero.
+
+Encoded scalars first item is a packet type number (packet tag). The meaning of
+any other item(s) of the payload depends on the packet tag.
+
+Packet definitions
+
+	{wpt00Header int, typ int, s string}
+		typ:	Must be zero (ACIDFiler0 file).
+		s:	Any comment string, empty string is okay.
+
+		This packet must be present only once - as the first packet of
+		a WAL file.
+
+	{wpt00WriteData int, b []byte, off int64}
+		Write data (WriteAt(b, off)).
+
+	{wpt00Checkpoint int, sz int64}
+		Checkpoint (Truncate(sz)).
+
+		This packet must be present only once - as the last packet of
+		a WAL file.
+
+*/
+
+package lldb
+
+//TODO optimize bitfiler/wal/2pc data above final size