Autotools: added boost detection (only enabled if syncevolution is).
Autotools: added boost detection (only enabled if syncevolution is).

Unfortunately boost lacks any form of pkg-config integration; ideally,
syncevolution would drag boost-base as its dependency, but I couldn't
quickly find a way for this to happen, so we're doing it here for the
moment.

simo5/evolution-activesync,simo5/evolution-activesync,simo5/evolution-activesync