introduce LZ4_DISTANCE_MAX build macro

make it possible to generate LZ4-compressed block
with a controlled maximum offset (necessarily <= 65535).

This could be useful for compatibility with decoders
using a very limited memory budget (<64 KB).

Answer #154
diff --git a/doc/lz4_manual.html b/doc/lz4_manual.html
index 1c6dba7..ef1a8b5 100644
--- a/doc/lz4_manual.html
+++ b/doc/lz4_manual.html
@@ -396,6 +396,7 @@
   Note : initialization fails if size and alignment conditions are not respected.
          In which case, the function will @return NULL.
   Note2: An LZ4_stream_t structure guarantees correct alignment and size.
+  Note3: Before v1.9.0, use LZ4_resetStream() instead
  
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