Update all built-in VFSes to return SQLITE_OK for the
SQLITE_FCNTL_SYNC_OMITTED file-control operation.  Also change the 
xFileControl methods to return SQLITE_NOTFOUND for unrecognized
operation codes.

FossilOrigin-Name: 6f2c72a0f6579db3f40c079436ca40e3e52bd6d9
diff --git a/src/main.c b/src/main.c
index 4b93a2b..88dfcf0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -816,7 +816,7 @@
     /* SQLITE_INTERRUPT   */ "interrupted",
     /* SQLITE_IOERR       */ "disk I/O error",
     /* SQLITE_CORRUPT     */ "database disk image is malformed",
-    /* SQLITE_NOTFOUND    */ 0,
+    /* SQLITE_NOTFOUND    */ "unknown operation",
     /* SQLITE_FULL        */ "database or disk is full",
     /* SQLITE_CANTOPEN    */ "unable to open database file",
     /* SQLITE_PROTOCOL    */ "locking protocol",
@@ -2364,6 +2364,8 @@
         rc = SQLITE_OK;
       }else if( fd->pMethods ){
         rc = sqlite3OsFileControl(fd, op, pArg);
+      }else{
+        rc = SQLITE_NOTFOUND;
       }
       sqlite3BtreeLeave(pBtree);
     }