Fix void* <=> protocol casts. Fix of tests.

test/test_suite/dynamic/null_and_protocol.c3t

@@ -0,0 +1,37 @@
+module test;
+import std::io;
+import std::time;
+
+protocol Test {}
+
+fn void main()
+{
+	Test* a;
+	bool x = a == null;
+	a = null;
+	any* z = a;
+	z = null;
+}
+
+/* #expect: test.ll
+
+%"any*" = type { ptr, i64 }
+@"$ct.void" = linkonce global %.introspect { i8 0, i64 0, ptr null, i64 1, i64 0, i64 0, [0 x i64] zeroinitializer }, align 8
+
+define void @test.main() #0 {
+entry:
+  %a = alloca %"any*", align 8
+  %x = alloca i8, align 1
+  %z = alloca %"any*", align 8
+  store %"any*" zeroinitializer, ptr %a, align 8
+  %0 = getelementptr inbounds %"any*", ptr %a, i32 0, i32 0
+  %1 = load ptr, ptr %0, align 8
+  %eq = icmp eq ptr %1, null
+  %2 = zext i1 %eq to i8
+  store i8 %2, ptr %x, align 1
+  store %"any*" { ptr null, i64 ptrtoint (ptr @"$ct.void" to i64) }, ptr %a, align 8
+  %3 = load %"any*", ptr %a, align 8
+  store %"any*" %3, ptr %z, align 8
+  store %"any*" { ptr null, i64 ptrtoint (ptr @"$ct.void" to i64) }, ptr %z, align 8
+  ret void
+}