Simplified test for common codecs

Ignore-this: 50fa4b03c6cb3089037ca56aa160f7bd

darcs-hash:20121012114713-b22ec-0e07dd86ed80f3d30b3a27b8dd79f9dda4675272
Increased core version

Ignore-this: fe0e79413ff961edd0a0597530c31a15

darcs-hash:20121012120301-b22ec-657b8936637a5c5d706401ad605d19a2913cc5bb