Protect internal method in Process

Author: chrisseaton

src/main/ruby/core/process.rb

@@ -200,6 +200,7 @@ def self.nanoseconds_to_unit(nanoseconds, unit)
       raise ArgumentError, "unexpected unit: #{unit}"
     end
   end
+  private_class_method :nanoseconds_to_unit
 
   ##
   # Sets the process title. Calling this method does not affect the value of