Solution: Use the current one from ctrlspace 5.0 + minor style fixes
Problem: CtrlSpace 5.0 does no longer work with airline
Solution: Modify the ctrlspace extension to call the new APIs
The statusline work fine but the custom ctrlspace function
somehow/somewhere gets overridden and I could not figure out where.
Therefore the user must add
let g:CtrlSpaceStatuslineFunction = "airline#extensions#ctrlspace#statusline()"
to its .vimrc.
Problem: Ctrlspace 5.0 does not integrate well into tabline
Solution: Write a tabline extensions for ctrlspace 5.0.
The extensions is capable of showing both tabs and buffers, but only the
buffers of a current tab are shown.