Add speexdsp package

packages/speexdsp.rb

+require 'package'
+
+class Speexdsp < Package
+  description 'Speex is an Open Source/Free Software patent-free audio compression format designed for speech.'
+  homepage 'https://speex.org/'
+  version '1.2rc3'
+  source_url 'http://downloads.xiph.org/releases/speex/speexdsp-1.2rc3.tar.gz'
+  source_sha256 '4ae688600039f5d224bdf2e222d2fbde65608447e4c2f681585e4dca6df692f1'
+
+  def self.build
+    system "./configure --prefix=#{CREW_PREFIX} --libdir=#{CREW_LIB_PREFIX}"
+    system "make"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end