add size_t to FFI usable types, print better error message in 'lookupCType'
add size_t to FFI usable types, print better error message in 'lookupCType'

darcs-hash:cb50c3d881f627ff2206f56acb7122ad27f40338

dpwright/jhc,dpwright/jhc,dpwright/jhc,dpwright/jhc