added ZSTD_initStaticDCtx()

doc/zstd_manual.html

@@ -691,6 +691,22 @@ size_t ZSTD_CDict_loadDictionary(ZSTD_CDict* cdict, const void* dict, size_t dic
 </b><p>  Create a ZSTD decompression context using external alloc and free functions 
 </p></pre><BR>
 
+<pre><b>ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);
+</b><p>  workspace: The memory area to emplace the context into.
+             Provided pointer must 8-bytes aligned.
+             It must outlive context usage.
+  workspaceSize: Use ZSTD_estimateDCtxSize() or ZSTD_estimateDStreamSize()
+                 to determine how large workspace must be to support scenario.
+ @return : pointer to ZSTD_DCtx*, or NULL if error (size too small)
+  Note : zstd will never resize nor malloc() when using a static dctx.
+         If it needs more memory than available, it will simply error out.
+  Note 2 : there is no corresponding "free" function.
+           Since workspace was allocated externally, it must be freed externally.
+  Limitation : currently not compatible with internal DDict creation,
+               such as ZSTD_initDStream_usingDict().
+ 
+</p></pre><BR>
+
 <pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
 </b><p>  Create a digested dictionary, ready to start decompression operation without startup delay.
   Dictionary content is simply referenced, and therefore stays in dictBuffer.