Fix broken spec

Broken since 8a38757. Stub a setting to keep the old code path being
exercised.
Fix (spurious) test failure on big-endian architectures

Our example includes a int_64_t value (the PDU's length prefix), which
is endian-sensitive and so needs to be asserted using native endianness.

Fixes:

  https://github.com/wincent/Command-T/issues/101
  https://bugzilla.redhat.com/show_bug.cgi?id=1130079