Crosscompilation fails due to incorrect case

[qjebbs]

Windows is case-insensitive, but when cross-compiling dmlc from Linux with the MinGW tools this causes problems, because the file is named shlwapi.h in lowercase.

include/dmlc/filesystem.h (L21)

#include <Shlwapi.h>
#pragma comment(lib, "Shlwapi.lib")

src/io/local_filesys.cc (L16)

#include <Windows.h>

same issue with this one: https://github.com/mattn/mruby-pcre-regexp/issues/7