The shared library feature in Makefile.host is no longer used.
Rip it off to keep the build infrastucture simple.

Update Documentation/kbuild/makefiles.txt too.
The section "4.3 Definition shared libraries" should be removed
and the following sections should be re-numbered.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>
Suggested-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NMichal Marek <mmarek@suse.cz>