Ignore --server and --client passed to JRuby directly.

These flags are normally processed by the JRuby launcher (either
the native one or the bash script) and turned into a -server or
-client flag passed to the underlying JVM. However, -server and
-client never did anything on 64-bit JVMs and have no effect on
OpenJDK 7+. So in general, these flags do nothing, but many older
programs still try to pass them to JRuby.

When passed directly to org.jruby.Main, these flags caused an
error because we expected them to be processed out of the arg list
by the launchers. Since they're practically no-ops now, and since
they make largely zero-sum configuration changes at the JVM level,
I think it's fine to ignore them if they sneak into the argument
list.
Merge remote-tracking branch 'github/master'