Support autodetection of ARM assembly.

autoload/arm/ft.vim

@@ -0,0 +1,20 @@
+let s:cpo_save = &cpo
+set cpo&vim
+
+function! arm#ft#FTarm()
+  let head = ' '.getline(1).' '.getline(2).' '.getline(3).' '.getline(4).
+	\' '.getline(5).' '
+  " Can't use setf, as we need to overrule the default filetype setting
+  if matchstr(head, '\s\.arch\s\+armv4') != ''
+    set filetype=armv4
+  elseif matchstr(head, '\s\.arch\s\+armv5') != ''
+    set filetype=armv5
+  elseif matchstr(head, '\s\.arch\s\+arm') != ''
+    set filetype=arm
+  elseif matchstr(head, '\s\.cpu\s\+arm') != ''
+    set filetype=arm
+  endif
+endfunction
+
+let &cpo = s:cpo_save
+unlet s:cpo_save