Deprecate taint/trust and related methods, and make the methods no-ops

This removes the related tests, and puts the related specs behind
version guards.  This affects all code in lib, including some
libraries that may want to support older versions of Ruby.

spec/ruby/library/delegate/delegator/taint_spec.rb

@@ -6,18 +6,20 @@ describe "Delegator#taint" do
     @delegate = DelegateSpecs::Delegator.new("")
   end
 
-  it "returns self" do
-    @delegate.taint.equal?(@delegate).should be_true
-  end
+  ruby_version_is ''...'2.7' do
+    it "returns self" do
+      @delegate.taint.equal?(@delegate).should be_true
+    end
 
-  it "taints the delegator" do
-    @delegate.__setobj__(nil)
-    @delegate.taint
-    @delegate.tainted?.should be_true
-  end
+    it "taints the delegator" do
+      @delegate.__setobj__(nil)
+      @delegate.taint
+      @delegate.tainted?.should be_true
+    end
 
-  it "taints the delegated object" do
-    @delegate.taint
-    @delegate.__getobj__.tainted?.should be_true
+    it "taints the delegated object" do
+      @delegate.taint
+      @delegate.__getobj__.tainted?.should be_true
+    end
   end
 end

spec/ruby/library/delegate/delegator/trust_spec.rb

@@ -6,17 +6,19 @@ describe "Delegator#trust" do
     @delegate = DelegateSpecs::Delegator.new([])
   end
 
-  it "returns self" do
-    @delegate.trust.equal?(@delegate).should be_true
-  end
+  ruby_version_is ''...'2.7' do
+    it "returns self" do
+      @delegate.trust.equal?(@delegate).should be_true
+    end
 
-  it "trusts the delegator" do
-    @delegate.trust
-    @delegate.untrusted?.should be_false
-  end
+    it "trusts the delegator" do
+      @delegate.trust
+      @delegate.untrusted?.should be_false
+    end
 
-  it "trusts the delegated object" do
-    @delegate.trust
-    @delegate.__getobj__.untrusted?.should be_false
+    it "trusts the delegated object" do
+      @delegate.trust
+      @delegate.__getobj__.untrusted?.should be_false
+    end
   end
 end

spec/ruby/library/delegate/delegator/untaint_spec.rb

@@ -6,19 +6,21 @@ describe "Delegator#untaint" do
     @delegate = -> { DelegateSpecs::Delegator.new("") }.call
   end
 
-  it "returns self" do
-    @delegate.untaint.equal?(@delegate).should be_true
-  end
+  ruby_version_is ''...'2.7' do
+    it "returns self" do
+      @delegate.untaint.equal?(@delegate).should be_true
+    end
 
-  it "untaints the delegator" do
-    @delegate.untaint
-    @delegate.tainted?.should be_false
-    # No additional meaningful test; that it does or not taint
-    # "for real" the delegator has no consequence
-  end
+    it "untaints the delegator" do
+      @delegate.untaint
+      @delegate.tainted?.should be_false
+      # No additional meaningful test; that it does or not taint
+      # "for real" the delegator has no consequence
+    end
 
-  it "untaints the delegated object" do
-    @delegate.untaint
-    @delegate.__getobj__.tainted?.should be_false
+    it "untaints the delegated object" do
+      @delegate.untaint
+      @delegate.__getobj__.tainted?.should be_false
+    end
   end
 end

spec/ruby/library/delegate/delegator/untrust_spec.rb

@@ -6,18 +6,20 @@ describe "Delegator#untrust" do
     @delegate = DelegateSpecs::Delegator.new("")
   end
 
-  it "returns self" do
-    @delegate.untrust.equal?(@delegate).should be_true
-  end
+  ruby_version_is ''...'2.7' do
+    it "returns self" do
+      @delegate.untrust.equal?(@delegate).should be_true
+    end
 
-  it "untrusts the delegator" do
-    @delegate.__setobj__(nil)
-    @delegate.untrust
-    @delegate.untrusted?.should be_true
-  end
+    it "untrusts the delegator" do
+      @delegate.__setobj__(nil)
+      @delegate.untrust
+      @delegate.untrusted?.should be_true
+    end
 
-  it "untrusts the delegated object" do
-    @delegate.untrust
-    @delegate.__getobj__.untrusted?.should be_true
+    it "untrusts the delegated object" do
+      @delegate.untrust
+      @delegate.__getobj__.untrusted?.should be_true
+    end
   end
 end