Add missing const.

src/pio_rpc.c

@@ -16,7 +16,7 @@
 
 
 struct clientBufSize
-computeClientStreamBufSize(int streamID, struct collSpec *collector)
+computeClientStreamBufSize(int streamID, const struct collSpec *collector)
 {
   /* 1 record is filled in last to indicate number of records in total */
   struct clientBufSize rmaSizeSpec

src/pio_rpc.h

@@ -101,7 +101,7 @@ struct collSpec
 };
 
 struct clientBufSize
-computeClientStreamBufSize(int streamID, struct collSpec *collector);
+computeClientStreamBufSize(int streamID, const struct collSpec *collector);
 
 #endif