Add gawk as a dependency for Ubuntu/Debian. Thanks @brainopia

Tested on Vagrant, VirtualBox, Chef-Solo, Ubuntu precise64 3.2.0-23-generic
apt-get installing gawk solves the issue, or simply running `rvm requirements` (both manual interventions)

```bash
INFO: Performing RVM install with [curl -L https://get.rvm.io | bash  -s -- --branch stable --version head] (as vagrant)
INFO: package[libxslt-dev] is a virtual package, actually acting on package[libxslt1-dev]
INFO: package[ncurses-dev] is a virtual package, actually acting on package[libncurses5-dev]
INFO: Building rvm_ruby[ruby-2.0.0-p247], this could take a while...
WARN: Failed to install rvm_ruby[ruby-2.0.0-p247]. Check logs in /log/ruby-2.0.0-p247
```

Thanks for the fix @brainopia !!!!