Rewrite fs.find_file test to pass on Windows
Rewrite fs.find_file test to pass on Windows

Todo: fix underlying issue with fs.split_base that caused
original version not working ("/" and "\" should be valid anchors
on Windows).

xpol/luacheck,mpeterv/luacheck,linuxmaniac/luacheck,mpeterv/luacheck,mpeterv/luacheck,xpol/luacheck,xpol/luacheck,linuxmaniac/luacheck