MacOSX: if we cannot use -undefined dynamic_lookup (such as on 10.2 or earlier)
we link extension directly against the dynamic library in the framework in
stead of against the framework. This will fix building extensions for 2.3
after 2.4 has been installed too.

to an empty value and distutils will get confused lateron.

implementation features better error reporting, and better compliance
with the PEP.

  something (overridable through Install-command entry)
- Hidden status is now determined by flavor == hidden, not by
  missing Download-URL. Hidden packages behave like installer packages.
- Made some error messages a bit more understandable.

Because there's new functionality the version has been upped to 0.5.

in no way affect library or include directories the code must take that into
account and not assume some options were found.

prevent leaving zombies.

(Removed at Ping's request.)

(Contributed by Jiwon Seo.)

LDFLAGS and CPPFLAGS for library and include directories, respectively.  Solves
issue of either env var containing other options that do not pertain to the
directories being searched for.