[FIX,INTERNAL] fix align_extend for infixOfInfix again

git-svn-id: http://svn.seqan.de/seqan/trunk@14629 e6417c60-b987-48fd-844e-b20f0fcc1017
[TEST] Added a test scenario for the align_extend module

git-svn-id: http://svn.seqan.de/seqan/trunk@14630 e6417c60-b987-48fd-844e-b20f0fcc1017