RFR JDK-8037781: Remove sun.misc.Regexp* classes

[Pavel Rappo]

Hi everyone,

could you please review my change for JDK-8037781: http://cr.openjdk.java.net/~chegar/8037781/webrev.00/

After JDK-8035158 was fixed we freed our hands to remove these 4 classes: 

	1. sun.misc.RegexpPool, 
	2. sun.misc.RegexpTarget, 
	3. sun.misc.Regexp, 
	4. sun.misc.REException 

The sole client class sun.net.spi.DefaultProxySelector relied on this private regex implementation for years. Now we broke this dependency and used public API instead: java.util.regex.* Thus those classes have no reasons to stay in jdk any more.

Thanks
-Pavel