Add yaml-cpp

Current contents:
  expat-2.1.0-4.fc18.x86_64.rpm
  fontconfig-2.10.2-2.fc18.x86_64.rpm
  freetype-2.4.10-4.fc18.x86_64.rpm
  zlib-1.2.7-9.fc18.x86_64.rpm
  liberation-fonts-common-1.07.2-12.fc18.noarch.rpm
  liberation-mono-fonts-1.07.2-12.fc18.noarch.rpm
  liberation-sans-fonts-1.07.2-12.fc18.noarch.rpm
  liberation-serif-fonts-1.07.2-12.fc18.noarch.rpm
  libjpeg-turbo-1.2.90-1.fc18.x86_64.rpm
  boost-filesystem-1.53.0-14.fc19.x86_64.rpm
  boost-devel-1.53.0-14.fc19.x86_64.rpm
  boost-static-1.53.0-14.fc19.x86_64.rpm
  boost-system-1.53.0-14.fc19.x86_64.rpm
  yaml-cpp-0.5.1-1.fc20.x86_64.rpm
  yaml-cpp-devel-0.5.1-1.fc20.x86_64.rpm

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>