MSVC in cmake has always been a boolean variable ( see https://cmake.org/cmake/help/latest/variable/MSVC.html)
detecting the MSVC Compiler requires therefore "if (MSVC)"

further, the MSVC Compiler will always emit '199711L' for __cplusplus, if it is called without the option '/Zc:__cplusplus'

this odd behavior will break any version check in the headers.
e.g. './include/boost/parser/detail/text/detail/begin_end.hpp' or 'boost/hana/traits.hpp

therefore "add_compile_options(/Zc:__cplusplus)" is always nrequired for the MSVC compiler

…rontend check

…14 version

…h pre 3.14 version"

This reverts commit eab545e.