Update to 7-Zip 17.01 Beta from Igor Pavlov

- Minor speed optimization for LZMA2 (xz and 7z) multi-threading compression.
  7-Zip now uses additional memory buffers for multi-block LZMA2 compression.
  CPU utilization was slightly improved.
- 7-zip now creates multi-block xz archives by default. Block size can be
  specified with -ms[Size]{m|g} switch.
- xz decoder now can unpack random block from multi-block xz archives.  7-Zip
  File Manager now can open nested multi-block xz archives (for example,
  image.iso.xz) without full unpacking of xz archive.
- 7-Zip now can create zip archives from stdin to stdout.
- 7-Zip command line: @listfile now doesn't work after -- switch.  Use
  -i@listfile before -- switch instead.

fixed bugs:
- 7-Zip could add unrequired alternate file streams to WIM archives, for
  commands that contain filename wildcards and -sns switch.
- 7-Zip 17.00 beta crashed for commands that write anti-item to 7z archive.
- 7-Zip 17.00 beta ignored "Use large memory pages" option.

C/Xz.c

@@ -1,5 +1,5 @@
 /* Xz.c - Xz
-2017-04-03 : Igor Pavlov : Public domain */
+2017-05-12 : Igor Pavlov : Public domain */
 
 #include "Precomp.h"
 
@@ -9,7 +9,7 @@
 #include "XzCrc64.h"
 
 const Byte XZ_SIG[XZ_SIG_SIZE] = { 0xFD, '7', 'z', 'X', 'Z', 0 };
-const Byte XZ_FOOTER_SIG[XZ_FOOTER_SIG_SIZE] = { 'Y', 'Z' };
+/* const Byte XZ_FOOTER_SIG[XZ_FOOTER_SIG_SIZE] = { 'Y', 'Z' }; */
 
 unsigned Xz_WriteVarInt(Byte *buf, UInt64 v)
 {
@@ -26,16 +26,16 @@ unsigned Xz_WriteVarInt(Byte *buf, UInt64 v)
 
 void Xz_Construct(CXzStream *p)
 {
-  p->numBlocks = p->numBlocksAllocated = 0;
-  p->blocks = 0;
+  p->numBlocks = 0;
+  p->blocks = NULL;
   p->flags = 0;
 }
 
 void Xz_Free(CXzStream *p, ISzAllocPtr alloc)
 {
   ISzAlloc_Free(alloc, p->blocks);
-  p->numBlocks = p->numBlocksAllocated = 0;
-  p->blocks = 0;
+  p->numBlocks = 0;
+  p->blocks = NULL;
 }
 
 unsigned XzFlags_GetCheckSize(CXzStreamFlags f)