The mmsystem.h header check didn't include windows.h so check fails even though mmsystem.h was present.

(the AutoOption class takes care of defining env['SAMPLERATE'] and HAVE_SAMPLERATE)

(drop conf.define('HAVE_CELT', ...) since the AutoOption class handles this)

No functional change, only whitespace.

This reverts commit 3087895772.

Some python implementations report "linux3" on newer kernels. Of course,
we'll have to set IS_LINUX for those, too.

As reported by Peter Nelson, waf's check_cfg sets HAVE_OPUS=1 if the
pkg-config check is successful, however, the code requires OPUS custom
headers.

So if a dev package without custom headers is installed, explicitly
reset HAVE_OPUS to 0 to fix the FTBFS.

Signed-off-by: Eliot Blennerhassett <Eliot@Blennerhassett.gen.nz>

CCFLAGS isn't honoured at all, the proper name is CFLAGS.

conf.write_config_header() defaults to remove=True, so conf.defines() is
empty afterwards. Consequently, config.h is empty, too.

Set remove to False, so calling it another time for 32_64 builds works.

Closes: #21

Patch by Adam Conrad <adconrad@canonical.com>, taken from Ubuntu's
jackd2 package.

Fixes linkage errors as described in

   http://permalink.gmane.org/gmane.comp.audio.jackit/25841

Tested by Debian on hurd-i386, kfreebsd-amd64 and kfreebsd-i386.

In new waf, defines are no longer added to the conf environment, they
only end up in config.h. Consequently, they can't be referenced later
from the wscript.

So explicitly put ADDON_DIR to conf.env.