Better msvc compiler setup compatibility.
Better msvc compiler setup compatibility.

1. Use vcvarsall.bat if exists.
2. Use vcvars32.bat / vcvars64.bat if exists.
3. Do no compiler env setup in luarocks.bat if 1 and 2 are both not exists.

xpol/luavm,robooo/luarocks,keplerproject/luarocks,robooo/luarocks,starius/luarocks,ignacio/luarocks,tarantool/luarocks,robooo/luarocks,xpol/luarocks,starius/luarocks,starius/luarocks,ignacio/luarocks,ignacio/luarocks,luarocks/luarocks,xpol/luarocks,xpol/luainstaller,xpol/luavm,starius/luarocks,keplerproject/luarocks,tarantool/luarocks,xpol/luavm,keplerproject/luarocks,robooo/luarocks,xpol/luainstaller,keplerproject/luarocks,xpol/luarocks,xpol/luavm,xpol/luainstaller,ignacio/luarocks,luarocks/luarocks,xpol/luarocks,xpol/luavm,luarocks/luarocks,tarantool/luarocks,xpol/luainstaller