HTTPHeader.content_range throws error on non-byte units

* Added a nil check in Net::HTTPHeader#initialize_http_header for keys in the header that do not have any value
* Returning nil from the content_range method instead of raising an error when the unit in the content-range header is not bytes
* Modified initialize_http_header to match trunk

fix [Bug #11450]
fix https://github.com/ruby/ruby/pull/1018

lib/net/http/header.rb

@@ -338,8 +338,8 @@ module Net::HTTPHeader
   # fits inside the full entity body, as range of byte offsets.
   def content_range
     return nil unless @header['content-range']
-    m = %r<bytes\s+(\d+)-(\d+)/(\d+|\*)>i.match(self['Content-Range']) or
-        raise Net::HTTPHeaderSyntaxError, 'wrong Content-Range format'
+    m = %r<bytes\s+(\d+)-(\d+)/(\d+|\*)>i.match(self['Content-Range'])
+    return nil if m.nil?
     m[1].to_i .. m[2].to_i
   end
 

test/net/http/test_httpheader.rb

@@ -308,6 +308,14 @@ class HTTPHeaderTest < Test::Unit::TestCase
   end
 
   def test_content_range
+    @c['Content-Range'] = "bytes 0-499/1000"
+    assert_equal 0..499, @c.content_range
+    @c['Content-Range'] = "bytes 1-500/1000"
+    assert_equal 1..500, @c.content_range
+    @c['Content-Range'] = "bytes 1-1/1000"
+    assert_equal 1..1, @c.content_range
+    @c['Content-Range'] = "tokens 1-1/1000"
+    assert_equal nil, @c.content_range
   end
 
   def test_range_length
@@ -317,6 +325,8 @@ class HTTPHeaderTest < Test::Unit::TestCase
     assert_equal 500, @c.range_length
     @c['Content-Range'] = "bytes 1-1/1000"
     assert_equal 1, @c.range_length
+    @c['Content-Range'] = "tokens 1-1/1000"
+    assert_equal nil, @c.range_length
   end
 
   def test_chunked?