make upgrade/downgrade work for fusion sequences. New design, upgrade/downgrade aren't extension points anymore, but rather model_of is correctly defined to do 'the right thing', i.e. keeping the same register size. There might be compile-time overhead fixable by a smarter implementation or factorization with vector_of.
 unused typedef in gammaln
Merge pull request #804 from jtlap/warn_in_euler

 unused typedef in gammaln
remove unused include in gammaln
Merge pull request #805 from MetaScale/issue_802

make upgrade/downgrade work for fusion sequences. New design, upgrade/do...
replace strings by policies in qr documentation
missing std_pair fusion adapter include in upgrade unit test
qr3_2 benchmark was incorrect, in economy size mode permutations are returned as integers, use matrix mode