Disable cat*() on CloudABI. Also make tiny cleanups.

On a new platform that I am working on
(https://github.com/NuxiNL/cloudlibc) I am not implementing the
cat{open,close,gets}() API, just like Android, Newlib, etc.

Instead of adding yet another operating system name to the #ifs,
introduce _LIBCPP_HAS_CATOPEN in include/__config. Also adjust the code
to only pull in nl_types.h when _LIBCPP_HAS_CATOPEN is set. We only
needed this header for the cat*() API.

Differential Revision:	http://reviews.llvm.org/D8163
Reviewed by:	marshall


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@231937 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed