remote_bitbang: Add Windows support

remote_bitbang: Add Windows support

Windows socket descriptor is not file descriptor, so when
using remote_bitbang on Windows, it fails with "fdopen:
failed to open write stream".

This patch removes the file write stream, replaces it
with socket write calls.

Change-Id: Ifd7c8a4139a5ac51ecd2846835a7a947a90fe16c
Signed-off-by: Yun Liu <liuyun.97@gmail.com>
Reviewed-on: http://openocd.zylin.com/6096
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>