* NAR archives: handle files larger than 2^32 bytes. Previously it

would just silently store only (fileSize % 2^32) bytes.
* Use posix_fallocate if available when unpacking archives.
* Provide a better error message when trying to unpack something that
  isn't a NAR archive.

src/libutil/serialise.hh

@@ -106,6 +106,9 @@ string readString(Source & source);
 StringSet readStringSet(Source & source);
 
 
+MakeError(SerialisationError, Error)
+
+
 }