Using gsplit makes repo-creation fail

[mawkish]

When creating a repos you use gsplit if it's there, else split:

    let splitter = executable('gsplit') ? 'gsplit' : 'split'
    exe 'silent ! ' . splitter . ' -l 5000 -d --additional-suffix .txt ' . l:doc . ' ' . l:doc_path . a:doc

On my system at least (Fedora), gsplit doesn't have a -l flag:

gsplit: invalid option '-l'

... so repos fail to get created. Just changing stuff to only split is used makes everything work OK.