Update to the latest SCons AsciiDoc tool.
README: simplify a link.
SConstruct: add "NDEBUG" to "CPPDEFINES".

Add "NDEBUG" to CPPDEFINES instead of CCFLAGS, since it is, after all, a C
pre-processor definition.
Ensure that Python is >=2.5, update manual.
Override mex $COMPFLAGS on Windows.

The Windows equivalent to the $CFLAGS variable is the $COMPFLAGS variable, which
makes overriding the mex compiler flags on Windows behave more like on a Unix
system
compile_msndfile: handle Mac and Unix together.
Docs: add a missing closing parentheses.
Docs: bump copyright year.
Add a ChangeLog entry for the coming 1.1 release.
TODO: postpone some features.

I will make a release before getting to implementing msndfile.write and
msndfile.blockwrite.