Reduce peak memory usage of Octave function read_cshort_binary

Attempts to read large amounts of data with 'read_cshort_binary' may
make Octave 6.0.0 overflow and exit with the message:
'octave exited with signal 6'.
The purpose of this change is to use more sparingly memory in order
to avoid overflowing in cases where the computer *does* have enough
memory to perform the desired operation.

Author: Imad-Eddine Srairi

gr-utils/octave/read_cshort_binary.m

@@ -42,5 +42,8 @@
   else
     v = fread (f, count, 'short');
     fclose (f);
-    cv = v(1:2:end)+v(2:2:end)*j;
+    v_r = v(1:2:end);
+    v_i = v(2:2:end)*j;
+    clear v;
+    cv = v_r+v_i;
   end