RFR 8065783: DCMD parser fails to recognize one character argument when it's positioned last

[Jaroslav Bachorik]

Please, review the following change

Issue : https://bugs.openjdk.java.net/browse/JDK-8065783
Webrev: http://cr.openjdk.java.net/~jbachorik/8065783/webrev.00

Currently, the DCMD parser fails to recognize the trailing one character 
long arguments. This is caused by the parser ignoring the last character 
when immediately following a delimiter char.

The fix itself consists of checking whether the last character is indeed 
a delimiter char (src/share/vm/services/diagnosticFramework.cpp#68).

The rest of the patch deals with testing - the WhiteBox support needs to 
be enhanced to handle DCMD arguments (currently only options) and custom 
delimiters (currently only comma).

Thanks,

-JB-