Variables by these names are only used from the local wscript and when
running "waf configure", which already for other reasons only can run at
the top-level.
These variables are thus not mandatory and not used.
Previously this was inherited via PBD.
On MacOS/X, this adds
"-undefined dynamic_lookup -flat_namespace"
and various "-framework .." options to linkflags
Without this flag, .dylibs fail to link usually because
of missing `-lintl` (Undefined symbols: "_libintl_dgettext")
On other systems this is a NO-OP:
CFLAGS_OSX, CXXFLAGS_OSX and LINKFLAGS_OSX
are only set on the darwin platform.
uselib is no longer implicit (inherited by .use). This is still incomplete,
some uselibs for non-linux variants may be missing.
bld.is_defined("HAVE_XXX") also no longer works and will have to be
changed (I think to bld.env["HAVE_XXX"]) in countless places.
Those objects do not have a versioned API by themselves.
This fixes issues with duplicate deployment (OSX, Linux bundles: cp) and
ardour listing control-surfaces multiple times (file index plugin dir).
This avoids having to define define LIBFOO_DLL=1 all over the place. If we ever go with static libs we will
need to define LIBFOO_STATIC=1 but hopefully in some central location like the top level wscript.
Oh, and I also dropped support for gcc older than version 4.x because ardour will already not build
on such an old version.
