Description of problem:
GC logging java opts are not passed to standalone server

Steps to Reproduce:
1. Start the standalone server (on windows or linux) and observe the console logs.

Actual results:
JAVA_OPTS: -server -XX:+UseCompressedOops -server -XX:+UseCompressedOops -Xms64m -Xmx512m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true

Expected results:
JAVA_OPTS: -server -XX:+UseCompressedOops -server -XX:+UseCompressedOops -Xms64m -Xmx512m -Djava.net.preferIPv4Stack=true -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true -verbose:gc -Xloggc:"$JBOSS_LOG_DIR/gc.log" -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=3M -XX:-TraceClassUnloading

Additional info:

• EAP6 jira: https://issues.jboss.org/browse/EAP6-121
• EAP6-121 feature is commented in standalone.sh and standalone.bat
• these OPTS are missing: -verbose:gc -Xloggc:"$JBOSS_LOG_DIR/gc.log" -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=3M -XX:-TraceClassUnloading