clean up how symbols are defined.

autoload/airline/extensions/branch.vim

@@ -3,8 +3,7 @@
 
 let s:empty_message = get(g:, 'airline#extensions#branch#empty_message',
       \ get(g:, 'airline_branch_empty_message', ''))
-let s:symbol = get(g:, 'airline#extensions#branch#symbol',
-      \ get(g:, 'airline_branch_prefix', get(g:, 'airline_powerline_fonts', 0) ? ' ' : ''))
+let s:symbol = g:airline_symbols.branch
 
 let s:has_fugitive = exists('*fugitive#head')
 let s:has_fugitive_detect = exists('*fugitive#detect')
@@ -28,7 +27,7 @@ function! airline#extensions#branch#get_head()
     endif
   endif
 
-  return empty(head) ? s:empty_message : s:symbol.head
+  return empty(head) ? s:empty_message : s:symbol.' '.head
 endfunction
 
 function! airline#extensions#branch#init(ext)

autoload/airline/extensions/readonly.vim

@@ -1,15 +0,0 @@
-" MIT License. Copyright (c) 2013 Bailey Ling.
-" vim: et ts=2 sts=2 sw=2
-
-let s:symbol = get(g:, 'airline#extensions#readonly#symbol',
-      \ get(g:, 'airline_readonly_symbol', get(g:, 'airline_powerline_fonts', 0) ? '' : 'RO'))
-
-function! airline#extensions#readonly#get_mark()
-  return &ro ? s:symbol : ''
-endfunction
-
-function! airline#extensions#readonly#init()
-  let g:airline_section_gutter = ' %#airline_file#%{airline#extensions#readonly#get_mark()} '
-        \ .g:airline_section_gutter
-endfunction
-

autoload/airline/extensions/whitespace.vim

@@ -10,9 +10,7 @@ else
   let s:show_message = get(g:, 'airline#extensions#whitespace#show_message', 1)
 endif
 
-let s:symbol = get(g:, 'airline#extensions#whitespace#symbol',
-      \ get(g:, 'airline_whitespace_symbol', get(g:, 'airline_powerline_fonts', 0) ? '✹' : '!'))
-
+let s:symbol = g:airline_symbols.whitespace
 let s:checks = get(g:, 'airline#extensions#whitespace#checks', ['indent', 'trailing'])
 
 let s:trailing_format = get(g:, 'airline#extensions#whitespace#trailing_format', 'trailing[%s]')