Vagrant: fix mount of shared folders

gistfile1.sh

# Environment
#
# OS: Mac OS X 10.9
# Vagrant: 1.5.1
# Box: precise64


# Error
#
# Failed to mount folders in Linux guest. This is usually because
# the "vboxsf" file system is not available. Please verify that
# the guest additions are properly installed in the guest and
# can work properly. The command attempted was:
#
# mount -t vboxsf -o uid=`id -u vagrant`,gid=`getent group vagrant | cut -d: -f3` /vagrant /vagrant
# mount -t vboxsf -o uid=`id -u vagrant`,gid=`id -g vagrant` /vagrant /vagrant

# login; run this; logout & reload
sudo ln -s /opt/VBoxGuestAdditions-4.3.10/lib/VBoxGuestAdditions /usr/lib/VBoxGuestAdditions