Put individual WebCL validator tests in the correct build system folder
WebCLArguments.cpp: Define ssize_t on MSVC++
check-empty-memory: Add missing <string> include

Almost everything was present from other headers on MSVC++, but not
operator==
tests: Use llvm::sys::TimeValue instead of <sys/time.h>

The latter is not available on Windows/MSVC++
tests: Take some Windows platform helpers from clang's lit.cfg
tests: Look for tool binaries in the LLVM_TOOLS_DIR with lit params sub'd

Thus, they are found even on Win32, where the binary location changes at
build time based on the selected configuration
WebCLArguments.cpp: Also use win32 path separators when building with MSVC++

Otherwise we get a lot of "Can't create temporary file" errors
kernel-runner: Use stack space more conservatively
radix-sort: Use cl_ basic type typedefs for kernel args

Otherwise 32-bit builds are broken as (unsigned) long will be different
size in C++ and OpenCL
Don't use sort(1) in tests, instead use FileCheck's order insensitive CHECK-DAG

Because `sort` on Windows is usually a crappy Microsoft impl which
doesn't respect LANG
Add VS2012 build instructions to README
Merge pull request #52 from ollisal/vs11

Windows / Visual Studio 2012 fixes