new formula: ODB C++ Object-Relational Mapping(ORM)

Now ODB compiler is built from source.

The remain problem is I must use this command to install the formula
brew install odb --env=std since I use homebrew gcc.

Can I avoid it?

@adamv @mikemcquaid @mistydemeo 
Add this to the existing CXXFLAGS instead:

```ruby
ENV.append "CXXFLAGS", "-fno-devirtualize"
```