Update meson build system

NOTE: This commit only tested on Linux (Ubuntu 18.04). Windows
build may not work as expected.

* Use meson >= 0.47.0 cause we use install_man function
* Add three helper Python script:
  * CopyFile.py: To copy file
  * CreateSymlink.py: To make symlink (both Windows and Unix)
  * GetZstdLibraryVersion.py: Parse lib/zstd.h to get zstd version
  These help emulating equivalent functions in CMake and Makefile.
* Use subdir from meson to split meson.build
  * Add contrib build
  * Fix other build
* Add new build options
  * build_programs: Enable programs build
  * build_contrib: Enable contrib build
  * build_tests: Enable tests build
  * use_static_runtime: Link to static run-time libraries on MSVC
  * zlib_support: Enable zlib support
  * lzma_support: Enable lzma support

contrib/meson/CopyFile.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+# #############################################################################
+# Copyright (c) 2018-present    lzutao <taolzu(at)gmail.com>
+# All rights reserved.
+#
+# This source code is licensed under both the BSD-style license (found in the
+# LICENSE file in the root directory of this source tree) and the GPLv2 (found
+# in the COPYING file in the root directory of this source tree).
+# #############################################################################
+import os
+import sys
+import shutil
+
+
+def usage():
+    print('usage: python3 CreateSymlink.py <src> <dst>')
+    print('Copy the file named src to a file named dst')
+    sys.exit(1)
+
+
+def main():
+    if len(sys.argv) < 3:
+        usage()
+    src = sys.argv[1]
+    dst = sys.argv[2]
+
+    if os.path.exists(dst):
+            print ('File already exists: %r' % (dst))
+            return
+
+    shutil.copy2(src, dst)
+
+
+if __name__ == '__main__':
+    main()