bzip2: Restore fix for unused variables

The commit "bzip2: Disable Borland warnings" accidentally reverted
changes from commit "Fix warnings for unused variables".  This restores
them.

Utilities/cmbzip2/bzlib.c

@@ -102,6 +102,7 @@ static
 void* default_bzalloc ( void* opaque, Int32 items, Int32 size )
 {
    void* v = malloc ( items * size );
+  (void)opaque;
    return v;
 }
 
@@ -109,6 +110,7 @@ static
 void default_bzfree ( void* opaque, void* addr )
 {
    if (addr != NULL) free ( addr );
+  (void)opaque;
 }
 
 
@@ -1505,6 +1507,7 @@ int BZ_API(BZ2_bzwrite) (BZFILE* b, void* buf, int len )
 /*---------------------------------------------------*/
 int BZ_API(BZ2_bzflush) (BZFILE *b)
 {
+  (void) b;
    /* do nothing now... */
    return 0;
 }