Add Vim guisp colors for spell highlights.
Add Vim guisp colors for spell highlights.

MacVim and assumingly other GUI versions would use the default colors
for these. This didn't look very nice, at least not with Ocean.

forivall/base16-builder,forivall/base16-builder,forivall/base16-builder,enosys/base16-builder,blockloop/base16-builder,Maximus5/base16-builder,idleberg/base16-builder,chriskempson/base16-builder,blockloop/base16-builder,jilen/base16-builder,enosys/base16-builder,hakatashi/base16-builder,hakatashi/base16-builder,pickfire/base16-builder,jilen/base16-builder,rail44/base16-builder,idleberg/base16-builder,idleberg/base16-builder,pickfire/base16-builder,chriskempson/base16-builder,Maximus5/base16-builder,pickfire/base16-builder,jaredru/base16-builder,jaredru/base16-builder,blockloop/base16-builder,chriskempson/base16-builder,Maximus5/base16-builder,jaredru/base16-builder,hakatashi/base16-builder,rail44/base16-builder,rail44/base16-builder,jilen/base16-builder,enosys/base16-builder