Replace list.h with its own version

Replace list.h with its own version

We copied include/list.h from Linux kernel, and it's of course in
GPLv2.  This has raised concerns to many people, as it's not clear
whether such a code is considered to be completely trivial, thus it
might be seen as a derivative work, which takes effect in GPL, as
suggested by Clemens.

For clearing the situation, this patch replaces the existing list.h
implementation from a new version.  The API is kept to be compatible,
but the codes were written from full scratch under LGPL, to be aligned
with other alsa-lib codes.

Reported-by: Clemens Lang <clemens.lang@bmw-carit.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>