Fix for PR libgcj/7416:
	* javax/naming/InitialContext.java (init): Use
	gnu.classpath.home.url.
	* java/security/Security.java: Use new properties.
	(loadProviders): Accept base url; use it.
	* java/lang/System.java: Document gnu.classpath.vm.shortname, and
	gnu.classpath.home.url.
	(gnu.classpath.home.url): Define.
	(gnu.classpath.vm.shortname): Likewise.

From-SVN: r60722