[Windows]Fix a bug which cause GDB.exe assert when try to run the inferior

[Eli Zaretskii]

> Date: Fri, 21 Feb 2014 15:03:31 +0800
> From: Yao Qi <yao@codesourcery.com>
> CC: <gdb-patches@sourceware.org>
> 
> 2014-02-21  Yuanhui Zhang  <asmwarrior@gmail.com>
> 
> 	* windows-nat.c (windows_xfer_shared_libraries): Return
> 	TARGET_XFER_EOF if LEN is zero.

Indeed.  May I also suggest to point to the details of the underlying
problem, or include its summary, in the ChangeLog entry?