Review request: JDK-6518827 (process) zero length Process arguments ignored on win32

[Alexey Utkin]

Bug description:
     https://jbs.oracle.com/bugs/browse/JDK-6518827
     http://bugs.sun.com/view_bug.do?bug_id=6518827

Here is the suggested fix:
http://cr.openjdk.java.net/~uta/openjdk-webrevs/JDK-6518827/webrev.00/

Summary:
     Here we close the long-standing problem of the lost empty argument.
Due to significant impact for legacy applications, the functionality
is not active by default and needs the presence of the Security
Manager, or defined in "false" the system property
     "jdk.lang.Process.allowAmbiguousCommands"
Currently the property has the "true" value by default.

We need to declare, that the property could change the default
value in the next major release. Please, read 7u21, 7u25, 7u40
release notes for details.

By introducing the dependence from property value we are stimulating
developer for more accurate approach for argument transfer and 
minimizing the regression risk.

New feature has the test coverage.

Regards,
-uta