FEAT: empty? to accept typesets

It was already accepting bitsets, so why not to support typesets too. Added a few `typeset!` unit tests (not complete)

src/boot/actions.r

@@ -140,7 +140,7 @@ head?: action [
 
 tail?: action [
 	{Returns TRUE if series is at or past its end; or empty for other types.}
-	series [series! gob! port! bitset! map!]
+	series [series! gob! port! bitset! typeset! map!]
 ]
 
 past?: action [

src/core/t-typeset.c

@@ -254,6 +254,10 @@
 		VAL_TYPESET(val) = ~VAL_TYPESET(val);
 		return R_ARG1;
 
+	case A_TAILQ:
+		// Necessary to make EMPTY? work:
+		return (VAL_TYPESET(val) == 0) ? R_TRUE : R_FALSE;
+
 	default:
 		Trap_Action(REB_TYPESET, action);
 	}

src/mezz/mezz-series.r

@@ -14,7 +14,7 @@ REBOL [
 empty?: make :tail? [
 	[
 		{Returns TRUE if empty or NONE, or for series if index is at or beyond its tail.}
-		series [series! object! gob! port! bitset! map! none!]
+		series [series! object! gob! port! bitset! typeset! map! none!]
 	]
 ]
 

src/tests/run-tests.r3

@@ -40,6 +40,7 @@ dt [ ;- delta time
 	wrap load %units/image-test.r3
 	wrap load %units/file-test.r3
 	wrap load %units/func-test.r3
+	wrap load %units/typeset-test.r3
 
 	recycle/torture
 	recycle

src/tests/units/typeset-test.r3

@@ -0,0 +1,42 @@
+Rebol [
+	Title:   "Rebol3 typeset! test script"
+	Author:  "Oldes, Peter W A Wood"
+	File: 	 %typeset-test.r3
+	Tabs:	 4
+	Needs:   [%../quick-test-module.r3]
+]
+
+~~~start-file~~~ "typeset"
+
+===start-group=== "typeset!"
+	--test-- "make typeset!"
+		--assert  typeset? types: make typeset! [block! map! object!]
+	--test-- "find in typeset"
+		--assert  find types block!
+		--assert  find types map!
+		--assert  find types object!
+		--assert  not find types string!
+
+	--test-- "union of typesets"
+		types2: union types make typeset! [string!]
+		--assert  typeset? types2
+		--assert  find types2 string!
+
+	--test-- "complement of typesets"
+		not-types: complement types
+		--assert typeset? not-types
+		--assert find not-types integer!
+
+	--test-- "difference of typesets"
+		types3: difference types make typeset! [object!]
+		--assert typeset? types3
+		--assert not find types3 object!
+
+	--test-- "empty typeset test"
+		;@@ requested: https://github.com/red/REP/issues/55
+		--assert  empty? make typeset! []
+		--assert  not empty? types
+
+===end-group===
+
+~~~end-file~~~