Simplification of PRAGMA integrity_check logic. Make sure that the depth

of the right-most subtree is correct.  Size reduction and performance increase,
with no change in output.

FossilOrigin-Name: 550705fcb64e7ad637686e47cabe2621d65851bf

src/pager.c

@@ -6387,12 +6387,14 @@ u8 sqlite3PagerIsreadonly(Pager *pPager){
   return pPager->readOnly;
 }
 
+#ifdef SQLITE_DEBUG
 /*
 ** Return the number of references to the pager.
 */
 int sqlite3PagerRefcount(Pager *pPager){
   return sqlite3PcacheRefCount(pPager->pPCache);
 }
+#endif
 
 /*
 ** Return the approximate number of bytes of memory currently