Changes toward being abld to process indexes on expressions. Not there yet -

this check-in is just movement in that direction.  Some tests are failing.

FossilOrigin-Name: 0ad0f8d77d8f95ca2ffb7745d18219f5e87dc89c

src/sqliteInt.h

@@ -2391,6 +2391,7 @@ struct NameContext {
 #define NC_IsCheck   0x0004  /* True if resolving names in a CHECK constraint */
 #define NC_InAggFunc 0x0008  /* True if analyzing arguments to an agg func */
 #define NC_PartIdx   0x0010  /* True if resolving a partial index WHERE */
+#define NC_IdxExpr   0x0020  /* True if resolving columns of CREATE INDEX */
 #define NC_MinMaxAgg 0x1000  /* min/max aggregates seen.  See note above */
 
 /*