[build] support --enable-tests, disable by default
[build] support --enable-tests, disable by default

directhex/banshee-hacks,eeejay/banshee,ixfalia/banshee,Dynalon/banshee-osx,mono-soc-2011/banshee,Dynalon/banshee-osx,dufoli/banshee,Dynalon/banshee-osx,lamalex/Banshee,ixfalia/banshee,mono-soc-2011/banshee,arfbtwn/banshee,babycaseny/banshee,arfbtwn/banshee,directhex/banshee-hacks,ixfalia/banshee,babycaseny/banshee,lamalex/Banshee,stsundermann/banshee,eeejay/banshee,arfbtwn/banshee,ixfalia/banshee,eeejay/banshee,lamalex/Banshee,dufoli/banshee,arfbtwn/banshee,Carbenium/banshee,lamalex/Banshee,allquixotic/banshee-gst-sharp-work,stsundermann/banshee,directhex/banshee-hacks,stsundermann/banshee,allquixotic/banshee-gst-sharp-work,mono-soc-2011/banshee,babycaseny/banshee,petejohanson/banshee,ixfalia/banshee,petejohanson/banshee,Dynalon/banshee-osx,eeejay/banshee,Carbenium/banshee,arfbtwn/banshee,babycaseny/banshee,arfbtwn/banshee,GNOME/banshee,allquixotic/banshee-gst-sharp-work,stsundermann/banshee,directhex/banshee-hacks,dufoli/banshee,stsundermann/banshee,stsundermann/banshee,petejohanson/banshee,Dynalon/banshee-osx,Carbenium/banshee,arfbtwn/banshee,GNOME/banshee,lamalex/Banshee,allquixotic/banshee-gst-sharp-work,GNOME/banshee,GNOME/banshee,Carbenium/banshee,GNOME/banshee,babycaseny/banshee,directhex/banshee-hacks,dufoli/banshee,mono-soc-2011/banshee,stsundermann/banshee,arfbtwn/banshee,Dynalon/banshee-osx,ixfalia/banshee,Dynalon/banshee-osx,GNOME/banshee,petejohanson/banshee,Carbenium/banshee,mono-soc-2011/banshee,dufoli/banshee,ixfalia/banshee,Carbenium/banshee,babycaseny/banshee,stsundermann/banshee,allquixotic/banshee-gst-sharp-work,dufoli/banshee,mono-soc-2011/banshee,eeejay/banshee,petejohanson/banshee,allquixotic/banshee-gst-sharp-work,ixfalia/banshee,dufoli/banshee,dufoli/banshee,mono-soc-2011/banshee,petejohanson/banshee,lamalex/Banshee,babycaseny/banshee,Dynalon/banshee-osx,GNOME/banshee,babycaseny/banshee,directhex/banshee-hacks,GNOME/banshee