At branch 'doc-from-discord-boost-discussion-20170926'.
The build documentation and scripts were slightly out of date about
Boost. This commit makes a (probably interim) update to them.
(CMakeLists.txt|SConstruct): `wesnoth` won't build using Boost earlier
than '1.50.0'. Boost 1.50.0 changed the location of version 3 of Boost
filesystem, from 'boost/filesystem/v3/' (e.g. for
'using boost::filesystem::v3::path;') to 'boost/filesystem/' (e.g. for
'using boost::filesystem::path;', enforced since the very introduction
of 'src/filesystem_boost.cpp'), making it incompatible unless using
precompiler directives for supporting backwards versions of Boost
filesystem prior than '1.50.0'. Using Boost 1.50.0 (and 51, 52 etc.)
`wesnoth` is able build and run. I checked using `ldd` that I am right
about the run time environment.
INSTALL.md: Requirement of Boost libraries version up to date.
projectfiles/VC12/README.md: Requirement of Boost libraries up to
date, only the statement of which one is the minimum version, not the
rest of the build guide for Boost as requirement.
.gitignore: Add KDevelop backup documents.
