Update alpaka to 1.1.0

[chillenzer]

There were changes in the subtree (maybe because of auto-formatting or the like), so I had to

git rm -r alpaka/
git commit -m "Remove alpaka to pull the latest release"
GIT_AUTHOR_NAME="Third Party" GIT_AUTHOR_EMAIL="[email protected]" git subtree add --prefix alpaka [email protected]:alpaka-group/alpaka.git 1.1.0 --squash

PS: The tests and examples are compiling but not working in the current dev (and neither here), so no way to verify that's correct. See #247 and #249.