Summary
-------

Add a system property that can be used to enable/disable the XML Signature secure validation mode.

Problem
-------

The XML Signature secure validation mode can be enabled or disabled by setting the property "org.jcp.xml.dsig.secureValidation" with the `javax.xml.crypto.XMLCryptoContext.setProperty()` method. This requires a code change. It would be useful, especially for testing purposes, if there was an equivalent way of enabling or disabling the mode at runtime w/o having to change the application's code.


Solution
--------

Add a system property named "org.jcp.xml.dsig.secureValidation" that can be used to enable/disable the XML Signature secure validation mode. This property supersedes the `XMLCryptoContext` property value of the same name.

Specification
-------------

1. Make the following changes to the definition of the `jdk.xml.dsig.secureValidationPolicy` security property in the java.security file:

```
 #
 # The policy for the XML Signature secure validation mode. Validation of
-# XML Signatures that violate any of these constraints will fail. The
-# mode is enforced by default. The mode can be disabled by setting the
-# property "org.jcp.xml.dsig.secureValidation" to Boolean.FALSE with the
-# javax.xml.crypto.XMLCryptoContext.setProperty() method.
+# XML Signatures that violate any of these constraints will fail.
+# The mode can be enabled or disabled by setting the property
+# "org.jcp.xml.dsig.secureValidation" to Boolean.TRUE or Boolean.FALSE with
+# the javax.xml.crypto.XMLCryptoContext.setProperty() method, or by setting
+# the system property "org.jcp.xml.dsig.secureValidation" to "true" or
+# "false". Any other value for the system property is also treated as "false".
+# If the system property is set, it supersedes the XMLCryptoContext property
+# value.
+#
+# The secure validation mode is enabled by default.
 #
 #   Policy:
 #       Constraint {"," Constraint }
```

 1. Document the system property in the @implNote of the  `javax.xml.crypto.dsig.dom.DOMValidateContext` class description where it currently describes the secure validation property:


```
  * method). When enabled, validation of XML signatures are subject to
  * stricter checking of algorithms and other constraints as specified by the
  * <code>jdk.xml.dsig.secureValidationPolicy</code> security property.
+ * The mode can be disabled by setting the property to {@code Boolean.FALSE}.
+ * The mode can also be enabled or disabled by setting the
+ * {@systemProperty org.jcp.xml.dsig.secureValidation} system property to
+ * "true" or "false". Any other value for the system property is also treated
+ * as "false". If the system property is set, it supersedes the
+ * {@code DOMValidateContext} property value.
  *
```