Add the ALLBITS macro as a shorthand for "(Bitmask)(-1)".

FossilOrigin-Name: 91bd619d27e4d91510a187bbb88de961a31c8a2e
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index e9aab2e..ff4dbd4 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2353,6 +2353,7 @@
 */
 #define MASKBIT(n)   (((Bitmask)1)<<(n))
 #define MASKBIT32(n) (((unsigned int)1)<<(n))
+#define ALLBITS      ((Bitmask)-1)
 
 /*
 ** The following structure describes the FROM clause of a SELECT statement.