adds first version of the expanded as assembler from mikko

lib/elf/null_section.rb

@@ -0,0 +1,18 @@
+module Elf
+  class NullSection < Section
+    def initialize
+      super('')
+    end
+
+    def write(io)
+    end
+
+    def type
+      Elf::Constants::SHT_NULL
+    end
+
+    def alignment
+      0
+    end
+  end
+end