Made C's sizeof operator work with initialized void variables.

Added regression tests that check cc65's handling of void variables.

test/val/void-size1.c

@@ -0,0 +1,56 @@
+/*
+  !!DESCRIPTION!! Getting the size of a void-type variable (cc65 extension)
+  !!ORIGIN!!      cc65 regression tests
+  !!LICENCE!!     Public Domain
+  !!AUTHOR!!      Greg King
+*/
+
+static const void list1 = {
+    (char)1,
+    (char)2,
+    (char)3,
+    (char)4,
+    (char)5,
+    (char)6,
+    (char)7,
+    (char)8,
+    (char)9,
+    (char)0
+};
+
+static void list2 = {
+    1,
+    2,
+    3,
+    4,
+    5,
+    6,
+    7,
+    8,
+    9,
+    0
+};
+
+void list3 = {
+    (char)1,
+    (char)2,
+    (char)3,
+    (char)4,
+    &list1,
+    (char)6,
+    (char)7,
+    (char)8,
+    (char)9,
+    &list2
+};
+
+/* We know that the expression is constant; don't tell us. */
+
+#pragma warn (const-comparison, off)
+
+int main (void)
+{
+    return sizeof list1 != 10
+        || sizeof list2 != 20
+        || sizeof list3 != 12;
+}