Fix SetCurrentDirectoryA alias as "chdir" for _WIN32

Windows's SetCurrentDirectoryA returns non-zero for success, while *nix chdir
returns zero for success. The existing #define chdir SetCurrentDirectoryA for
_WIN32 ignored this, causing the program to fail on Windows. Negating the
return value in the macro definition fixes this.
committing subversion revision 8595 by FloSoft
Merge in upstream bzr r8592 (svn r8595)

Merged in upstream fix of bug https://bugs.launchpad.net/s25rttr/+bug/1101789
(the macro which aliased Windows's SetCurrentDirectoryA to chdir did not
account for the inverted return value).