Maintaining boost cxx11abi packages

Nobody has claimed this yet.

@tmpsantos (in https://github.com/mapbox/mason/pull/268) has figured out how to build cxx11abi packages for boost libraries on travis 🎉 .

The key is that we need to edit the headers of the libstdc++ installed to enable the "duel API":

```bash
sudo perl -i -p -e "s/# define _GLIBCXX_USE_DUAL_ABI 0/# define _GLIBCXX_USE_DUAL_ABI 1/g;" /usr/include/x86_64-linux-gnu/c++/5/bits/c++config.h
```

per https://github.com/mapbox/mason/issues/157#issuecomment-272378928

Then one can set `-D_GLIBCXX_USE_CXX11_ABI=1` and it is respected and will no longer default to `0`.

Now we need to think through how to keep these maintained.

TODO:

- [ ] Does the boost new release script work?
https://github.com/mapbox/mason/blob/master/utils/new_boost.sh
- [ ] Other existing cxx11abi packages need be ported to be built on travis (rather than manually pushed) (notably gtest - refs https://github.com/mapbox/mason/pull/209)
- [ ] Do we want to maintain cxx11abi packages for all boost libraries?

Start with utils/new_boost.sh and the Travis build approach described in the issue. Check whether the Boost release script works for cxx11abi packages, then review the existing gtest package and mapbox/mason#209 for the porting pattern. Done means deciding the Boost coverage and moving the relevant existing packages from manual publishing to Travis builds.

Written by the indexing model from the issue text.