initial support for Bus types

bs/Types.bs

@@ -0,0 +1,15 @@
+package Types(
+    Pc, Insn, Addr,
+    Byte, HalfWord, FullWord, DoubleWord, QuadWord
+    )
+    where
+
+type Byte       = UInt 8
+type HalfWord   = UInt 16
+type FullWord   = UInt 32
+type DoubleWord = UInt 64
+type QuadWord   = UInt 128
+type Insn       = FullWord
+
+type Pc         = DoubleWord
+type Addr       = DoubleWord