[ruby/resolv] Fix centimeters representation in Resolv::LOC::Size#to_s

`Size` smaller than 1m was represented as rational.
```ruby
Resolv::LOC::Size.create("0.01m").to_s #=> "1/100m"
```
Fix to represent in the proper form for `create`.

ruby/resolv@2ff9e0585d

Author: nobu

lib/resolv.rb

@@ -3305,8 +3305,8 @@ def initialize(scalar)
       attr_reader :scalar
 
       def to_s # :nodoc:
-        s = @scalar.unpack("H2").join.to_s
-        return ((s[0].to_i)*(10**(s[1].to_i-2))).to_s << "m"
+        s, = @scalar.unpack("C")
+        return "#{(s >> 4) * (10.0 ** ((s & 0xf) - 2))}m"
       end
 
       def inspect # :nodoc:

test/resolv/test_resource.rb

@@ -45,6 +45,7 @@ def test_size_create
   private def assert_size(input, base, power)
     size = Resolv::LOC::Size.create(input)
     assert_equal([(base << 4) + power], size.scalar.unpack("C"))
+    assert_equal(size, Resolv::LOC::Size.create(size.to_s))
   end
 
   def test_coord