[12] RFR (S) 8205417: Obsolete UnlinkSymbolsALot debugging option

[coleen.phillimore at oracle.com]

Summary: Obsolete and remove support for UnlinkSymbolsALot

open webrev at http://cr.openjdk.java.net/~coleenp/8205417.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8205417

Tested manually, with test/hotspot/jtreg/runtime/CommandLine, and mach5 
hs-tier1,2.

$ java -XX:+UnlinkSymbolsALot -version
Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option 
UnlinkSymbolsALot; support was removed in 12.0
java version "12-internal" 2019-03-19
Java(TM) SE Runtime Environment 19.3 (fastdebug build 
12-internal+0-2018-07-05-1710252.coleen.12unlink-symbols)
Java HotSpot(TM) 64-Bit Server VM 19.3 (fastdebug build 
12-internal+0-2018-07-05-1710252.coleen.12unlink-symbols, mixed mode)

Thanks,
Coleen