Fix broken documentation links

lib/rubygems/psych_tree.rb

@@ -22,7 +22,7 @@ def visit_Hash(o)
       def register(target, obj)
       end
 
-      # This is ported over from the yaml_tree in 1.9.3
+      # This is ported over from the YAMLTree implementation in Ruby 1.9.3
       def format_time(time)
         if time.utc?
           time.strftime("%Y-%m-%d %H:%M:%S.%9N Z")

lib/rubygems/request_set/lockfile.rb

@@ -38,7 +38,7 @@ def initialize(message, column, line, path)
   end
 
   ##
-  # Creates a new Lockfile for the given +request_set+ and +gem_deps_file+
+  # Creates a new Lockfile for the given Gem::RequestSet and +gem_deps_file+
   # location.
 
   def self.build(request_set, gem_deps_file, dependencies = nil)

lib/rubygems/security/policy.rb

@@ -143,7 +143,7 @@ def check_root(chain, time)
   end
 
   ##
-  # Ensures the root of +chain+ has a trusted certificate in +trust_dir+ and
+  # Ensures the root of +chain+ has a trusted certificate in Gem::Security.trust_dir and
   # the digests of the two certificates match according to +digester+
 
   def check_trust(chain, digester, trust_dir)

lib/rubygems/source.rb

@@ -102,7 +102,7 @@ def update_cache?
   end
 
   ##
-  # Fetches a specification for the given +name_tuple+.
+  # Fetches a specification for the given Gem::NameTuple.
 
   def fetch_spec(name_tuple)
     fetcher = Gem::RemoteFetcher.fetcher