vim: add a medium CM build variant

CM profile is between SMALL and NORMAL (780K)
with syntax (colors) and utf8 (mbyte) support.

also set a swap directory compatible with CM,
to be able to load big files from stdin :
zcat /etc/NOTICE.html.gz | vim -

Change-Id: I8f1ce1956b4c204e6ecdc19525c78bae07a24aaa