User Manual: Wrong PPA name in Linux installation instructions

The Linux installation instructions at http://mixxx.org/manual/1.11/chapters/installation.html#installation-on-gnu-linux instruct to use "sudo apt-add-repository ppa:mixxx" to add the Mixxx PPA. This results in an error:

% sudo apt-add-repository ppa:mixxx
Cannot access PPA (https://launchpad.net/api/1.0/~mixxx/+archive/ppa) to get PPA information, please check your internet connection.

The correct PPA name should be "ppa:mixxx/mixxx" instead:

% sudo apt-add-repository ppa:mixxx/mixxx
You are about to add the following PPA to your system:

 More info: https://launchpad.net/~mixxx/+archive/mixxx
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmp5M3d4t/secring.gpg' created
gpg: keyring `/tmp/tmp5M3d4t/pubring.gpg' created
gpg: requesting key 4716DAB5 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmp5M3d4t/trustdb.gpg: trustdb created
gpg: key 4716DAB5: public key "Launchpad PPA for Mixxx Release Managers" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
OK

The documentation should be updated accordingly.