windows-untested: Fix paths to msvc_dbg.c/h

windows-untested: Fix paths to msvc_dbg.c/h

* windows-untested/vc60/gc.dsp (SOURCE): Fix paths to msvc_dbg.c and
msvc_dbg.h.
* windows-untested/vc60/libgc.dsp (SOURCE): Likewise.
* windows-untested/vc60/libgcmt.dsp (SOURCE): Likewise.
* windows-untested/vc60/libgcmt.dsp (File RelativePath): Likewise.
* windows-untested/vc70/libgc.vcproj (File RelativePath): Likewise.
* windows-untested/vc70/libgcmt.vcproj (File RelativePath): Likewise.
* windows-untested/vc71/gc.vcproj (File RelativePath): Likewise.
* windows-untested/vc71/libgc.vcproj (File RelativePath): Likewise.
* windows-untested/vc71/libgcmt.vcproj (File RelativePath): Likewise.