C++: Add DB scheme upgrade and downgrade scripts

cpp/downgrades/625f706f2a44ae8dc3fc168bfe2637e65c30b012/exprs.ql

@@ -0,0 +1,17 @@
+class Expr extends @expr {
+  string toString() { none() }
+}
+
+class Location extends @location_expr {
+  string toString() { none() }
+}
+
+predicate isExprWithNewBuiltin(Expr expr) {
+  exists(int kind | exprs(expr, kind, _) | 336 <= kind and kind <= 362)
+}
+
+from Expr expr, int kind, int kind_new, Location location
+where
+  exprs(expr, kind, location) and
+  if isExprWithNewBuiltin(expr) then kind_new = 1 else kind_new = kind
+select expr, kind_new, location

cpp/downgrades/625f706f2a44ae8dc3fc168bfe2637e65c30b012/upgrade.properties

@@ -0,0 +1,3 @@
+description: Add new builtin operations
+compatibility: partial
+exprs.rel: run exprs.qlo

cpp/ql/lib/upgrades/f96ad9b2da43bbc9e55a72a165febd270ae07981/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add new builtin operations
+compatibility: backwards