merged CCtx and CStream as a single same object

To be changed : ZSTD_sizeof_CCtx(), ZSTD_estimateCCtxSize()

doc/zstd_manual.html

@@ -244,6 +244,8 @@ size_t     ZSTD_freeDCtx(ZSTD_DCtx* dctx);
  
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+<pre><b>typedef ZSTD_CCtx ZSTD_CStream;  </b>/**< CCtx and CStream are effectively same object */<b>
+</b></pre><BR>
 <h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
 size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
 </pre></b><BR>