Revert "Move using directive from Job.h to Job.cpp" (r190902)

Seems like it was intentional to export ArgStringList as
driver::ArgStringList, and e.g. examples/clang-interpreter/main.cpp
uses it this way.

However, exporting it with a typedef seems like a more common way to do it.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190906 91177308-0d34-0410-b5e6-96231b3b80d8
Revert r190902 and r190906

The first one broke the build, and the latter one made it worse.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190907 91177308-0d34-0410-b5e6-96231b3b80d8
Claim compatibility with VS 2012 by default

This will define _MSC_VER to 1700 by default and avoid linker errors
from /failifmismatch linker directives in the C++ standard headers.

Most people trying out the Visual Studio integration are using 2012,
since that's the only version that clang-format works with.  This way
they don't have to pass funky -Xclang -fmsc-version=1700 flags just to
link against the standard C++ runtime.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190908 91177308-0d34-0410-b5e6-96231b3b80d8
Add comment about exporting clang::driver::ArgStringList,
as suggested by Jordan on IRC. Also, use the unqualified name
in Job.cpp.

And while we're here, refer to StringRef with the unqualified
name, because we have a using directive for that too.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@190909 91177308-0d34-0410-b5e6-96231b3b80d8