Add the SQLITE_DBSTATUS_CACHE_SIZE verb for sqlite3_db_status(). The

highwater mark does not yet work on this verb.

FossilOrigin-Name: 418c6d8113bc337556b0d47acfd6a7d865d1121f

src/pager.c

@@ -4854,6 +4854,16 @@ int sqlite3PagerRefcount(Pager *pPager){
   return sqlite3PcacheRefCount(pPager->pPCache);
 }
 
+/*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+int sqlite3PagerMemUsed(Pager *pPager){
+  int perPageSize = pPager->pageSize + pPager->nExtra + 20;
+  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+           + sqlite3MallocSize(pPager);
+}
+
 /*
 ** Return the number of references to the specified page.
 */