ports/134743: devel/Monotone and pthreaded dependencies

[Lapo Luchini]

Monotone is not multithreaded, but (as you told me) it better be linked
with -pthread if linked versus sqlite which depends on -pthread; right
now SQLite can be compiled both ways (with a negligible overhead, as far
as I know; but if I'm wrong please tell me) but monotone's configure
can't know that because `pkg-config sqlite3 --libs` doesn't advertise
that (it does that only when --static); always using -pthread is what's
done on other OSes (e.g. OpenBSD) and it's probably the easiest thing to
do in the short period, but (maybe) not the best one in the long period.

I'm adding mnag@ in Cc (as sqlite3 port maintainer) to ask him:
1. is it correct that `ldd /usr/local/lib/libsqlite3.so.8` shows libthr?
2. is it correct that `pkg-config sqlite3 --libs` doesn't advertise
pthreads? upstream as: http://www.sqlite.org/cvstrac/tktview?tn=3943
3. also, can you tell me how much (if at all) overhead there is using
SQLite with -pthreads in a program that's single-threaded? is it worth
having an OPTION for that?