configure: check for boost -mt libs

[martin-raden]

sometimes only the multi-threading libs are installed, which causes linking to the standard libs (without -mt suffix) to die..

in that case we might need something like this

LIBS="$LIBS -lboost_regex-mt -lboost_program_options-mt -lboost_filesystem-mt -lboost_system-mt -lboost_iostreams-mt -lz"