re-bootstrap on armel, armhf for 64-bit time_t transition

• d/control, d/rules: Only use dbus-broker on 64-bit architectures, plus i386

  This breaks a dependency cycle on the architectures affected by the 64-bit time_t transition: at-spi2-core, dbus-broker, systemd, cryptsetup, libssh, openssh-server, gtk+3.0, at-spi-2-core. It can be reverted after the transition has finished.

  Partially reopens: #998062
  Helps: #1066844

• d/control, d/rules: Temporarily skip tests on 32-bit except for i386

  This allows at-spi2-core to be re-bootstrapped on those architectures during the 64-bit time_t transition. It normally has a circular build-dependency on an older version of itself.

  Closes: #1066844

• Update changelog

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Bug number to be added.