Fixes for redirected-drive cut, mode, read/write

Several changes to drive redirection.  Most importantly, without this fix if you cut a folder from your redirected drive and paste it to the desktop, you'll lose all its contents.  This is because the RDP server requests that the drive be deleted *before* it does the copy.  mstsc treated this premature delete-pending request on the directory as an error; freerdp happily did as ordered and recursively deleted the directory and returned "success".

Also included in this patch:  it will set the file mode appropriately (assuming the filesystem on your redirected storage supports it!); also read and write will not fail if an interrupt is received or for EAGAIN/EINTR.

I recommend this both for stable-1.1 and master branches.