removed hard-copied Vienna{FVM,Mini,Math} -> switching to subtree'd approach
Squashed 'external/ViennaMini/' content from commit 01d80ba

git-subtree-dir: external/ViennaMini
git-subtree-split: 01d80ba332a5d5a2da68606f82d0ced358f354d7
Merge commit '778b66c577a4c6f66a7a027366e3c5653f9f001c' as 'external/ViennaMini'
Squashed 'external/ViennaMath/' content from commit fb470c0

git-subtree-dir: external/ViennaMath
git-subtree-split: fb470c0660c7ee068b596955d47e9643f75267e3
Merge commit 'b3d9d4ce5107b4973fc8208c24587c17ebb5e058' as 'external/ViennaMath'
removed ViennaMath to be able to retrieve it again from scratch
Squashed 'external/ViennaMath/' content from commit fb470c0

git-subtree-dir: external/ViennaMath
git-subtree-split: fb470c0660c7ee068b596955d47e9643f75267e3
Merge commit 'ffa91ff6c664f2fd07f462f870bfb4b49c0ce7a6' as 'external/ViennaMath'
fighting with subtree and ViennaMath  ..

after receiving the subtree, git complains that there are changes,
some changes in the benchmark example of ViennaMath .. dunno ..