loci: fix 32-bit build

GCC warned "this decimal constant is unsigned only in ISO C90" for large 32-bit
constants. Fixed by writing them in hex.
diff --git a/c_gen/codegen.py b/c_gen/codegen.py
index 0d7832a..cc4a58c 100644
--- a/c_gen/codegen.py
+++ b/c_gen/codegen.py
@@ -59,7 +59,7 @@
                         # Special case for version
                         pwtms.append(PushWireTypesMember(m.name, m.offset, m.length, "obj->version"))
                     else:
-                        pwtms.append(PushWireTypesMember(m.name, m.offset, m.length, m.value))
+                        pwtms.append(PushWireTypesMember(m.name, m.offset, m.length, hex(m.value)))
             type_members_by_version[version] = pwtms
 
         # Merge versions with identical type members