emboss: fix issue with X11

- Add an option to build without-x
- Add a `depends_on :x11` otherwise
- Add a `depends_on :libpng` that was missing.
- Add a `depends_on 'gd'` that is optional.
- Add a `depends_on 'libharu'` also optional for pdf output.
- Add a flag to enable 64bit pointers on 32bit machines.
- Add a flag to enable pthreads.

It's worth noting that this will build against mysql or postgresql.
It searches for `pg_config`. It's reasonable for molecular biology
grinding software have some sort of DB enabled. In that case,
we might want to add an `ENV :userpaths` to pick up the preferred
`pg_config` or we want to add a depends_on postgresql. Thoughts?

Fixes Homebrew/homebrew#15782

Closes Homebrew/homebrew#15817.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/emboss.rb

@@ -5,11 +5,24 @@ class Emboss < Formula
   url 'ftp://emboss.open-bio.org/pub/EMBOSS/EMBOSS-6.5.7.tar.gz'
   sha1 '907231eafe07917ae0bf9c5da2e7cdc3e9bae03a'
 
+  option 'without-x', 'Build without X11 support'
+
   depends_on 'pkg-config' => :build
+  depends_on 'libharu'    => :optional
+  depends_on 'gd'         => :optional
+  depends_on :libpng      => :recommended
+  depends_on :x11 unless build.include? 'without-x'
 
   def install
-    system "./configure", "--disable-debug", "--disable-dependency-tracking",
-                          "--prefix=#{prefix}"
-    system "make install"
+    args = %W[
+      --disable-debug
+      --disable-dependency-tracking
+      --prefix=#{prefix}
+      --enable-64
+      --with-thread
+    ]
+    args << '--without-x' if build.include? 'without-x'
+    system './configure', *args
+    system 'make install'
   end
 end