Experimental Symbol Capture Bin Input Throttle

Experimental Symbol Capture Bin Input Throttle
--throttle read speed when reading capture bin files that are still being written to by OP25, quick easy piggyback (-n).
Readme tweaks
Minor tweaks

include/dsd.h

@@ -592,6 +592,10 @@ typedef struct
   int fourv_counter[2]; //external reference counter for ESS_B fragment collection
   int p2_is_lcch; //flag to tell us when a frame is lcch and not sacch
 
+  //experimental symbol file capture read throttle
+  unsigned long long int symbol_throttle; //throttle speed
+  int use_throttle; //only use throttle if set to 1
+
   //dstar header for ncurses
   unsigned char dstarradioheader[41];