wrap screen redrawing in a function to try and avoid screen flicker
wrap screen redrawing in a function to try and avoid screen flicker

Some versions of gvim flicker when `redraw!` is used. Use `redraw` for
them and use `redraw!` for terminal vim.

Fixes #449

nikmartin/dotfiles,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup