bolt-gen: add truncated uint support for TLV fields

TLV's have truncated values, add support for them. plus
some 'compilation' tests.

tools/generate-bolts.py

@@ -153,10 +153,12 @@ class Type(FieldSet):
         'u16',
         'u32',
         'u64',
+        'tu16',
+        'tu32',
+        'tu64',
         'bool',
         'amount_sat',
         'amount_msat',
-        # FIXME: omits var_int
     ]
 
     typedefs = [
@@ -168,6 +170,12 @@ class Type(FieldSet):
         'secp256k1_ecdsa_signature',
     ]
 
+    truncated_typedefs = [
+        'tu16',
+        'tu32',
+        'tu64',
+    ]
+
     # Externally defined variable size types (require a context)
     varsize_types = [
         'peer_features',
@@ -238,6 +246,8 @@ class Type(FieldSet):
     def type_name(self):
         if self.name in self.typedefs:
             return self.name
+        if self.name in self.truncated_typedefs:
+            return self.name[1:]
         if self.is_enum:
             prefix = 'enum '
         else: