Add in-tree mspec and ruby/spec

* For easier modifications of ruby/spec by MRI developers.
* .gitignore: track changes under spec.
* spec/mspec, spec/rubyspec: add in-tree mspec and ruby/spec.
  These files can therefore be updated like any other file in MRI.
  Instructions are provided in spec/README.
  [Feature #13156] [ruby-core:79246]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58595 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/rubyspec/library/matrix/shared/transpose.rb

@@ -0,0 +1,19 @@
+require File.expand_path('../../fixtures/classes', __FILE__)
+require 'matrix'
+
+describe :matrix_transpose, shared: true do
+  it "returns a transposed matrix" do
+    Matrix[[1, 2], [3, 4], [5, 6]].send(@method).should == Matrix[[1, 3, 5], [2, 4, 6]]
+  end
+
+  it "can transpose empty matrices" do
+    m = Matrix[[], [], []]
+    m.send(@method).send(@method).should == m
+  end
+
+  describe "for a subclass of Matrix" do
+    it "returns an instance of that subclass" do
+      MatrixSub.ins.send(@method).should be_an_instance_of(MatrixSub)
+    end
+  end
+end