This patch does some housekeeping for the new <version> header.
It adds it to the module.modulemap, and the double_include.sh.cpp test.
Additionally it corrects the // UNSUPPORTED options for the libc++
specific test. The header needs to compile under C++03 to support
modules, and it should compile under all available compilers.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@329144 91177308-0d34-0410-b5e6-96231b3b80d8
