Cleaned up/simplified error-handling:

- DistutilsOptionError is now documented as it's actually used, ie.
    to indicate bogus option values (usually user options, eg. from
    the command-line)
  - added DistutilsSetupError to indicate errors that definitely arise
    in the setup script
  - got rid of DistutilsValueError, and changed all usage of it to
    either DistutilsSetupError or ValueError as appropriate
  - simplified a bunch of option get/set methods in Command and
    Distribution classes -- just pass on AttributeError most of
    the time, rather than turning it into something else

Lib/distutils/msvccompiler.py

@@ -360,6 +360,9 @@ class MSVCCompiler (CCompiler) :
             if extra_postargs:
                 ld_args.extend (extra_postargs)
 
+            print "link_shared_object():"
+            print "  output_filename =", output_filename
+            print "  mkpath'ing:", os.path.dirname (output_filename)
             self.mkpath (os.path.dirname (output_filename))
             self.spawn ([self.link] + ld_args)