Implement a picker for selecting an item class, using the editable string picker.

Used in special node editing and also item editing.

rsrc/dialogs/edit-item.xml

@@ -76,7 +76,7 @@
 	<text top='220' left='220' width='137' height='13'>Type flag: (0-1000)</text>
 	<text top='244' left='220' width='141' height='13'>Value: (0-10000)</text>
 	<text top='268' left='220' width='141' height='13'>Weight: (0-250)</text>
-	<text top='292' left='220' width='141' height='13'>Special class: (0-100)</text>
+	<button name='edit-ic' type='tiny' text-size='10' top='292' left='220' width='141' height='13'>Special class:</button>
 	<text name='missile-title' top='220' left='440' width='140' height='16'>Missile type:</text>
 	<field name='missile' top='243' left='463' width='50' height='16'/>
 	<pict name='missile-pic' type='missile' num='3' top='243' left='440'/>

rsrc/schemas/readme.md

@@ -312,6 +312,7 @@ subtags:
 names are used when showing the Pick Sound dialog in various places. The required `id`
 attribute specifies which sound it applies to.
 * `<event>` - (max unbounded) Gives a name to a major event flag. These names are shown (and editable) when showing the Pick Event dialog in various places. The required `id` attribute specifies which event.
+* `<item-class>` - (max unbounded) Gives a name to an item special class. These names are shown (and editable) when showing the Pick Item Class dialog in various places. The required `id` attribute specifies which class.
 
 Terrain Types
 -------------

rsrc/schemas/scenario.xsd

@@ -373,6 +373,15 @@
 					</xs:simpleContent>
 				</xs:complexType>
 			</xs:element>
+			<xs:element name="item-class" minOccurs="0" maxOccurs="unbounded">
+				<xs:complexType>
+					<xs:simpleContent>
+						<xs:extension base="xs:string">
+							<xs:attribute name="id" use="required" type="xs:integer"/>
+						</xs:extension>
+					</xs:simpleContent>
+				</xs:complexType>
+			</xs:element>
 		</xs:sequence>
 	</xs:complexType>
 	<xs:element name="scenario">