win32 porting for kobuki_driver.
remove garbage code.
extern sigslots templates to avoid multiple instantiation.
re-using access() to check existence of serial port
Revert "re-using access() to check existence of serial port"

This reverts commit acaa4597554639e7ad0e243775b681d9859f28e2.
modify checking connection in init of kobuki.
move location of class extern.
merge hydro-devel.
Merge branch 'hydro-devel' of https://github.com/yujinrobot/kobuki into win-porting
remove connection checking in the outside of serial object.
remove needless header(io.h).
Merge pull request #269 from yujinrobot/win-porting

Remove connection check of serial port