[serialization] Add support for ArrayTypes.

...in a quest for completeness. ArrayTypes don't actually work yet
(single-dimensional arrays are typed as slices), but when they do the test
that is currently XFAIL'd should start passing.

With this, all non-transient types can now be serialized and deserialized.

Swift SVN r6101

test/Serialization/array.swift

@@ -0,0 +1,16 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: %swift -emit-module -o %t/has_array.swiftmodule %S/Inputs/has_array.swift
+// RUN: llvm-bcanalyzer %t/has_array.swiftmodule | FileCheck %s
+// RUN: %swift -emit-silgen -I=%t %s -o /dev/null
+// XFAIL: *
+
+// CHECK-NOT: FALL_BACK_TO_TRANSLATION_UNIT
+
+import has_array
+
+fourByFour[3][3] = 42
+
+// NOTE: Do not add anything else to this test. It is intended to be a bare
+// minimum test for serializing ArrayType that should start passing as soon as
+// Parse, Sema, and SILGen can handle ArrayTypes.