PSA: C++11 libraries need to update their libraries.json and CMakeLists.txt

From: Peter Dimov (pdimov_at_[hidden])
Date: 2023-10-01 12:20:47

Libraries that now require C++11, such as Atomic, TypeIndex, LexicalCast,
need to update their libraries.json files to now state "cxxstd": 11, and
to add the C++11 requirement to their CMakeLists.txt files, e.g.

target_compile_features(boost_lexical_cast INTERFACE cxx_std_11)

boostdep --cmake looks at libraries.json and automatically adds the
above requirement, so for generated CMakeLists.txt files (such as the
one in lexical_cast), a simple regeneration with e.g.
`boostdep --cmake lexical_cast` will suffice.

Note that cxx_std_11 requires CMake 3.8, so the
cmake_minimum_required line may need to be adjusted as well.

(`boostdep --cmake` does that automatically.)