[PATCH] DocBook: only use tabular style for long synopsis

There was a complaint that function declarations are shown tabular in the
documentation since switching to xmlto.  This patch disables tabular mode
when the function fits in one line.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>