[boost] Feature/cmake-config merged to develop; yml files need to be updated

Subject: [boost] Feature/cmake-config merged to develop; yml files need to be updated
From: Peter Dimov (lists_at_[hidden])
Date: 2018-12-18 18:09:37

I've just merged the superproject branch feature/cmake-config to develop. 
This updates `b2 install` to export CMake configuration files into the 
`cmake` subdirectory of the library directory. These configuration files 
enable a Boost installation to be used from CMake via 
`find_package(boost_filesystem)`, without relying on FindBoost.

Unfortunately, this change adds two necessary submodules to the 
superproject, `tools/boost_install` and `libs/headers`. As a result, all 
.travis.yml and appveyor.yml files that rely on a partial checkout need to 
be updated to perform

    git submodule update --init tools/boost_install
    git submodule update --init libs/headers

in addition to the usual

    git submodule update --init tools/build
    git submodule update --init libs/config

I'm sorry for the inconvenience this will cause, or perhaps already has 
caused.