C#: Add DB upgrade and downgrade scripts.

csharp/downgrades/97da4e8c5750e07c4f7c8a366b21060e05ecd5ed/cil_type_annotation.ql

@@ -0,0 +1,11 @@
+class AnnotatedElement extends @cil_has_type_annotation {
+  string toString() { none() }
+}
+
+class Field extends @cil_field {
+  string toString() { none() }
+}
+
+from AnnotatedElement element, int annotation
+where cil_type_annotation(element, annotation) and not element instanceof Field
+select element, annotation

csharp/downgrades/97da4e8c5750e07c4f7c8a366b21060e05ecd5ed/type_annotation.ql

@@ -0,0 +1,11 @@
+class AnnotatedElement extends @has_type_annotation {
+  string toString() { none() }
+}
+
+class Field extends @field {
+  string toString() { none() }
+}
+
+from AnnotatedElement element, int annotation
+where type_annotation(element, annotation) and not element instanceof Field
+select element, annotation

csharp/downgrades/97da4e8c5750e07c4f7c8a366b21060e05ecd5ed/upgrade.properties

@@ -0,0 +1,4 @@
+description: Remove CIL fields as entities that can have type annotations and remove field type annotations.
+compatibility: backwards
+cil_type_annotation.rel: run cil_type_annotation.qlo
+type_annotation.rel: run type_annotation.qlo

csharp/ql/lib/upgrades/81a394bedda3d4747e36496c7be4d958424636d6/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add CIL fields as entities that can have type annotations.
+compatibility: backwards