mention if functions can be used near the colon

[jidanni]

On (info "(make) Functions") mention if functions can be used

Here:Or here
        As well as of course here

If so, add some examples, as currently they are all := examples,
and no : examples.

Also too bad we can't operate on $@ even though we already ought to know
it at this point:
%.bla:$(subst ...,...,$@)

P.S., in (info "(make) Concept Index") there is a listing for double
colon, but none for single colon. Nor in (info "(make) Name Index").

P.S., trailing blanks exist in (info "(make) Pattern Intro")
make 3.81-8

P.S., no fair asking me "what are you actually attempting to do?" as I
was just poking around.