[vim] new, experimental trailing space function and menu item

Visibility of listchars is handled by g:solarized_visibility
but on the cursorline they can still be hard to spot if cursorline
is on due to the cursorline background color.

This new trailing spaces function, available in the menu or via
emenu, should change the trailing space highlighting on only
the cursorline. It doesn't work in call cases as, for example,
the comments pattern in most syntaxes will override it.

colors/solarized.vim

@@ -4,7 +4,7 @@
 "           (see this url for latest release & screenshots)
 " License:  OSI approved MIT license (see end of this file)
 " Created:  In the middle of the night
-" Modified: 2011 May 04
+" Modified: 2011 May 05
 "
 " Usage "{{{
 "
@@ -219,6 +219,7 @@ call s:SetOption("termcolors",16)
 call s:SetOption("contrast","normal")
 call s:SetOption("visibility","normal")
 call s:SetOption("diffmode","normal")
+call s:SetOption("hitrail",0)
 call s:SetOption("menu",1)
 
 "}}}
@@ -937,6 +938,24 @@ hi! link pandocMetadataTitle             pandocMetadata
 "
 autocmd GUIEnter * if (s:vmode != "gui") | exe "colorscheme " . g:colors_name | endif
 "}}}
+" Highlight Trailing Space {{{
+" Experimental: Different highlight when on cursorline
+function! s:SolarizedHiTrail()
+    if g:solarized_hitrail==0
+        hi! clear solarizedTrailingSpace
+    else
+        syn match solarizedTrailingSpace "\s*$"
+        exe "hi! solarizedTrailingSpace " .s:fmt_undr .s:fg_red .s:bg_none .s:sp_red
+    endif
+endfunction  
+augroup SolarizedHiTrail
+    autocmd!
+    if g:solarized_hitrail==1
+        autocmd! Syntax * call s:SolarizedHiTrail()
+        autocmd! ColorScheme * if g:colors_name == "solarized" | call s:SolarizedHiTrail() | else | augroup! s:SolarizedHiTrail | endif
+    endif
+augroup END
+" }}}
 " Menus "{{{
 " ---------------------------------------------------------------------
 " Turn off Solarized menu by including the following assignment in your .vimrc:
@@ -989,6 +1008,9 @@ if g:colors_name == "solarized" && g:solarized_menu != 0
     amenu &Solarized.&Diff\ Mode.&Normal\ Diff\ Mode :let g:solarized_diffmode="normal"  \| colorscheme solarized<CR>
     amenu &Solarized.&Diff\ Mode.&High\ Diff\ Mode   :let g:solarized_diffmode="high"    \| colorscheme solarized<CR>
 
+    if g:solarized_hitrail==0 | let l:hitrailswitch="On" | else | let l:hitrailswitch="Off" | endif
+    exe "amenu &Solarized.&Experimental.&Turn\\ Highlight\\ Trailing\\ Spaces\\ ".l:hitrailswitch." :let g:solarized_hitrail=(abs(g:solarized_hitrail-1)) \\| colorscheme solarized<CR>"
+
     amenu &Solarized.&Help.&Solarized\ Help          :help solarized<CR>
     amenu &Solarized.&Help.&Toggle\ Background\ Help :help togglebg<CR>
     amenu &Solarized.&Help.&Removing\ This\ Menu     :help solarized-menu<CR>