when (pretty) pring a DT add extra space between columns if colnames contain spaces

[jan-glx]

For example, I find

        #ID(s) interactor A  ID(s) interactor B  Alt. ID(s) interactor A  Alt. ID(s) interactor B
     1:            unipr...            unipr...                 intac...                 intac...
     2:            unipr...            intac...                 intac...                 intac...
     3:            unipr...            intac...                 intac...                 intac...
     4:            unipr...            intac...                 intac...                 intac...
     5:            intac...            unipr...                 intac...                 intac...

much more readable than

        #ID(s) interactor A ID(s) interactor B Alt. ID(s) interactor A Alt. ID(s) interactor B
     1:            unipr...           unipr...                intac...                intac...
     2:            unipr...           intac...                intac...                intac...
     3:            unipr...           intac...                intac...                intac...
     4:            unipr...           intac...                intac...                intac...
     5:            intac...           unipr...                intac...                intac...

[MichaelChirico]

This could be handled by quote = TRUE, though it's worth noting that base doesn't fix this problem.