zbar: add JPEG-related patch

This patch was applied upstream, but has not yet made it into any
official release. Without this patch, libjpeg is unable to seek
within a JPEG datastream, resulting in hard-to-diagnose failures.

Closes Homebrew/legacy-homebrew#19291.

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

Formula/zbar.rb

@@ -11,6 +11,13 @@ class Zbar < Formula
   depends_on 'imagemagick'
   depends_on 'ufraw'
 
+  def patches
+    # fix JPEG handling using patch from
+    #   http://sourceforge.net/p/zbar/discussion/664596/thread/58b8d79b#8f67
+    # already applied upstream but not present in the 0.10 release
+    DATA
+  end
+
   def install
     args = %W[
       --disable-dependency-tracking
@@ -31,3 +38,27 @@ def install
     system "make install"
   end
 end
+
+__END__
+diff --git a/zbar/jpeg.c b/zbar/jpeg.c
+index fb566f4..d1c1fb2 100644
+--- a/zbar/jpeg.c
++++ b/zbar/jpeg.c
+@@ -79,8 +79,15 @@ int fill_input_buffer (j_decompress_ptr cinfo)
+ void skip_input_data (j_decompress_ptr cinfo,
+                       long num_bytes)
+ {
+-    cinfo->src->next_input_byte = NULL;
+-    cinfo->src->bytes_in_buffer = 0;
++    if (num_bytes > 0) {
++        if (num_bytes < cinfo->src->bytes_in_buffer) {
++            cinfo->src->next_input_byte += num_bytes;
++            cinfo->src->bytes_in_buffer -= num_bytes;
++        }
++        else {
++            fill_input_buffer(cinfo);
++        }
++    }
+ }
+
+ void term_source (j_decompress_ptr cinfo)