method_attr.rb: suppress warnings

* lib/rdoc/method_attr.rb (RDoc::MethodAttr#initialize_visibility):
  initialize to suppress warnings in #see, when called on a marshal
  loaded object.
test_rdoc_markup_pre_process.rb: input tempfile

* test/test_rdoc_markup_pre_process.rb (TestRDocMarkupPreProcess#setup):
  fix input_file_name, as the test script is not pre-processed.
options.rb: include root for out-place build

* lib/rdoc/options.rb (RDoc#finish): include root path in include
  paths, to work in another directory than the source directory.