make highlight link correctly for defined groups

[hiroebe]

When highlight groups CleverFCursor, CleverFChar, and CleverFDirect are defined by colorscheme (e.g. spring-night defines CleverFChar), g:clever_f_mark_*_color is ignored because highlight link does not overwrite them. So I think it should be highlight! link.

It was not correct. The expected behavior is:

• if g:clever_f_mark_*_color exists, highlight link should always be made with highlight! link
• else, highlight link should be made only when it has not done yet (by colorscheme) so use highlight link.

[hiroebe]

Test fails... I don't know much about vim plugins, but is it necessary to define these g:clefer_f_* variables by plugin-side even if they are not defined by user-side?

[rhysd]

Test fails... I don't know much about vim plugins, but is it necessary to define these g:cleferf* variables by plugin-side even if they are not defined by user-side?

Don't warry. I'll fix them after merge.

[hiroebe]

Thanks!