am ae4e1455: merge from open-source master

Merge commit 'ae4e14556bb3a789c4263ebba7ed42b3035e13f6' into kraken

* commit 'ae4e14556bb3a789c4263ebba7ed42b3035e13f6':
  Adapt to new location of libcore
  Make expr more POSIXy
  generic_x86 support
  Remove obsolete machine-setup.html reference.