Add win32 serial implementation

* src/configure.ac: add check for windows, and auto enable serial build

* src/serial/Makefile.in: use BUILD_FOR_WINDOWS flag to set OBJ sources of
  serial_class_win32.o or serial_class_lin.o

* src/serial/serial.cc: remove OS idependant file open flags

* src/serial/serial_class.h: include either serial_class_XXX.h depending
  on build OS.

* src/serial_class.cc: rename to serial_class_lin.cc

* src/serial_class.h: rename to serial_class_lin.h

* src/serial/serial_class_win32.cc: new file

* src/serial/serial_class_win32.h: new file
update configure