added ability to split input files for dictionary training

using command -B#
This is the same behavior as benchmark module,
which can also split input into arbitrary size blocks, using -B#.

doc/zstd_manual.html

@@ -845,6 +845,35 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
     </b>/* advanced parameters - may not remain available after API update */<b>
     ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
                               * even when referencing into Dictionary content (default:0) */
+    ZSTD_p_enableLongDistanceMatching=1200,  </b>/* Enable long distance matching.<b>
+                                         * This parameter is designed to improve the compression
+                                         * ratio for large inputs with long distance matches.
+                                         * This increases the memory usage as well as window size.
+                                         * Note: setting this parameter sets all the LDM parameters
+                                         * as well as ZSTD_p_windowLog. It should be set after
+                                         * ZSTD_p_compressionLevel and before ZSTD_p_windowLog and
+                                         * other LDM parameters. Setting the compression level
+                                         * after this parameter overrides the window log, though LDM
+                                         * will remain enabled until explicitly disabled. */
+    ZSTD_p_ldmHashLog,   </b>/* Size of the table for long distance matching, as a power of 2.<b>
+                          * Larger values increase memory usage and compression ratio, but decrease
+                          * compression speed.
+                          * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
+                          * (default: 20). */
+    ZSTD_p_ldmMinMatch,  </b>/* Minimum size of searched matches for long distance matcher.<b>
+                          * Larger/too small values usually decrease compression ratio.
+                          * Must be clamped between ZSTD_LDM_MINMATCH_MIN
+                          * and ZSTD_LDM_MINMATCH_MAX (default: 64). */
+    ZSTD_p_ldmBucketSizeLog,  </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
+                               * Larger values usually improve collision resolution but may decrease
+                               * compression speed.
+                               * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3). */
+    ZSTD_p_ldmHashEveryLog,  </b>/* Frequency of inserting/looking up entries in the LDM hash table.<b>
+                              * The default is MAX(0, (windowLog - ldmHashLog)) to
+                              * optimize hash table usage.
+                              * Larger values improve compression speed. Deviating far from the
+                              * default value will likely result in a decrease in compression ratio.
+                              * Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN. */
 
 } ZSTD_cParameter;
 </b></pre><BR>