Support for non standard port or unix socket will be available in next release.
Meanwhile you can replace these 2 files:
Specify non-standard port like this:
For unix socket use only the path in DB host field during install:
You can also try changing the driver Magento will access mysql in app/etc/config.xml:
There are driver types under <core_setup> (used during install/upgrade) and <core_write> (used during normal operation). Possible values are mysqli and pdo_mysql