Add syntax files from upstream vim repository

ftplugin/sass.vim

@@ -0,0 +1,27 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'vim') == -1
+  
+" Vim filetype plugin
+" Language:	Sass
+" Maintainer:	Tim Pope <vimNOSPAM@tpope.org>
+" Last Change:	2016 Aug 29
+
+" Only do this when not done yet for this buffer
+if exists("b:did_ftplugin")
+  finish
+endif
+let b:did_ftplugin = 1
+
+let b:undo_ftplugin = "setl com< cms< def< inc< inex< ofu< sua<"
+
+setlocal comments=://
+setlocal commentstring=//\ %s
+setlocal define=^\\s*\\%(@mixin\\\|=\\)
+setlocal includeexpr=substitute(v:fname,'\\%(.*/\\\|^\\)\\zs','_','')
+setlocal omnifunc=csscomplete#CompleteCSS
+setlocal suffixesadd=.sass,.scss,.css
+
+let &l:include = '^\s*@import\s\+\%(url(\)\=["'']\='
+
+" vim:set sw=2:
+
+endif