auctex: add HEAD

Closes Homebrew/homebrew#21202.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/auctex.rb

@@ -6,8 +6,12 @@ class Auctex < Formula
   mirror 'http://ftp.gnu.org/gnu/auctex/auctex-11.87.tar.gz'
   sha1 '0be92c7d8f89d57346fe07f05a1a045ffd11cd71'
 
+  head 'git://git.savannah.gnu.org/auctex.git'
+
   depends_on :tex
 
+  depends_on :autoconf if build.head?
+
   def options
     [['--with-emacs=</full/path/to/emacs>', "Force a different emacs"]]
   end
@@ -27,6 +31,8 @@ class Auctex < Formula
     brew_texmf = share + 'texmf'
     brew_texmf.mkpath
 
+    system "./autogen.sh" if build.head?
+
     system "./configure", "--prefix=#{prefix}",
                           "--with-texmf-dir=#{brew_texmf}",
                           "--with-emacs=#{which_emacs}",