bug#5846: 23.1.95.1 problems with mercurial commands in *VC Annotate* buffer on Windows

[Andy Moreton]

Using emacs from the pretest Windows binary:
http://alpha.gnu.org/gnu/emacs/pretest/windows/emacs-23.1.95-bin-i386.zip

In GNU Emacs 23.1.95.1 (i386-mingw-nt5.1.2600)
 of 2010-04-04 on G41R2F1
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags 
-Ic:/imagesupport/include'

Using Mercurial from TortoiseHg 0.9, which contains Mercurial-1.4, 
Python-2.5.4, PyGTK-2.12.1, GTK-2.16.1

Start emacs with "c:\emacs\23.1.95\bin\emacs -Q"
Open a file from a mercurial repository
Type "C-x v g" to annotate the file

In the *VC Annotate* buffer:
1) Type "l" (vc-annotate-show-log-revision-at-line)
   The Hg command runs, but the *vc-change-log* buffer is empty

2) Type "f" (vc-annotate-find-revision-at-line)
   Emacs displays a message "Cannot open load file: vc-nil"

These commands both work with emacs-23.1 with the same files.