Add test case using NULL and empty sequences

The parser does not parse these constructs properly but this demo shows
a workaround using constants defined in the ASN.1 model

tests/regression/test-emptysequence/Makefile

+include ../shared.mk
+
+all: test-ada test-llvm
+
+edit:
+	$(OPENGEODE) og.pr
+
+test-parse:
+	$(OPENGEODE) og.pr --check
+
+test-ada: 
+	$(OPENGEODE) og.pr --toAda
+	$(ASN1SCC) -Ada dataview.asn -typePrefix asn1Scc -equal
+	$(GNATMAKE) -O$(O) -c *.adb
+	$(GNATBIND) -n og.ali
+
+test-c: 
+	$(OPENGEODE) og.pr --toC
+	$(ASN1SCC) -c dataview.asn -typePrefix asn1Scc -equal
+	$(CC) -O$(O) -c *.c
+
+
+test-llvm:
+	$(OPENGEODE) og.pr --llvm -O$(O)
+	$(LLC) *.ll
+	$(CC) -O$(O) -c *.s
+
+
+coverage:
+	coverage run -p $(OPENGEODE) og.pr --toAda
+
+.PHONY: all edit test-parse test-ada test-llvm coverage

tests/regression/test-emptysequence/dataview.asn

+TASTE-Dataview DEFINITIONS ::=
+BEGIN
+
+EmptySeq ::= SEQUENCE {}
+
+NullType ::= NULL
+
+ChoiceWithEmptySeq ::= CHOICE {
+  a NULL,
+  b EmptySeq,
+  c NullType
+}
+
+c1 EmptySeq ::= {}
+
+n1 NullType ::= NULL
+
+c2 ChoiceWithEmptySeq ::= a: NULL
+c3 ChoiceWithEmptySeq ::= b: {}
+c4 ChoiceWithEmptySeq ::= c: NULL
+
+
+
+END

tests/regression/test-emptysequence/og.pr

+SYSTEM og;
+    /* CIF TEXT (159, 221), (287, 188) */
+    -- Text area for declarations and comments
+
+use dv comment 'dataview.asn';
+
+signal dd;
+signal we;
+    /* CIF ENDTEXT */
+    CHANNEL c
+        FROM ENV TO og WITH dd;
+        FROM og TO ENV WITH we;
+    ENDCHANNEL;
+    BLOCK og;
+        SIGNALROUTE r
+            FROM ENV TO og WITH dd;
+            FROM og TO ENV WITH we;
+        CONNECT c AND r;
+        /* CIF PROCESS (225, 49), (150, 75) */
+        PROCESS og;
+            /* CIF TEXT (57, 58), (331, 140) */
+            --  Test support for empty sequences and NULL type
+
+dcl empty1 EmptySeq := c1;
+
+dcl null1 NullType;
+
+dcl choice1 ChoiceWithEmptySeq;
+            /* CIF ENDTEXT */
+            /* CIF START (155, 216), (70, 35) */
+            START;
+                /* CIF TASK (132, 266), (115, 35) */
+                TASK empty1 := c1;
+                /* CIF TASK (118, 316), (144, 35) */
+                TASK choice1 := b: c1;
+                /* CIF NEXTSTATE (155, 366), (70, 35) */
+                NEXTSTATE wait;
+            /* CIF STATE (296, 231), (70, 35) */
+            STATE wait;
+                /* CIF INPUT (289, 286), (84, 35) */
+                INPUT dd;
+                    /* CIF OUTPUT (286, 336), (89, 35) */
+                    OUTPUT we;
+                    /* CIF NEXTSTATE (296, 386), (70, 35) */
+                    NEXTSTATE wait;
+            ENDSTATE;
+        ENDPROCESS og;
+    ENDBLOCK;
+ENDSYSTEM;
\ No newline at end of file