8023454: Updated DEVELOPER_README and command line flags, ensuring that undocumented flags that aren't guaranteed to work (disabled by default) and that are work in progress show up with an EXPERIMENTAL tag.
Reviewed-by: attila, jlaskey
syntax: glob
^.hgtip
build/*
dist/*
/nbproject/private/
private.xml
private.properties
webrev/*
webrev.zip
.classpath
*.class
*.clazz
*.log
*.orig
genfiles.properties
hotspot.log
.DS_Store*
TEST-*.xml
TESTS-*.xml
report.xml
CC/*
jcov2/*
.idea/*
test/lib/testng.jar
test/script/external/*
.project