RFR (S): 8129786: Buffer overrun when passing long not existing option in JDK 9

[Dmitry Dmitriev]

Hello,

Please review this small fix and new test. Also, I need a sponsor for 
this fix, who can push it.

In this fix logic for stripped_argname was put into "if (arg_len <= 
BUFLEN)" statement. stripped_argname is used only to check is option is 
newly obsolete. Since valid VM option should be not bigger than 255 
characters(BUFLEN value), then obsolete_jvm_flags contains only options 
with strlen <= BUFLEN.

Webrev: http://cr.openjdk.java.net/~ddmitriev/8129786/webrev.00/ 
<http://cr.openjdk.java.net/%7Eddmitriev/8129786/webrev.00/>
JBS: https://bugs.openjdk.java.net/browse/JDK-8129786
Tested: JPRT(with new test), hotspot all & vm.quick

Thanks,
Dmitry