RFR 8144906: Fix jshell's ToolBasicTest

[Jan Lahoda]

Hello,

The ToolBasicTest is @ignored now, as it fails on some platforms. I am 
proposing a partial fix for that, the patch is available here:
http://cr.openjdk.java.net/~jlahoda/8144906/webrev.00/

Notes:
-currently, there are three communication channels between the 
RemoteAgent process and the main JShell process: the command socket and 
RemoteAgent's out and err. The problem is that it is not easy to 
synchronize events between these channels, so it may happen that the 
command is already finished, while the out and err has not been fully 
processed yet. My proposal here is to change the System.out and 
System.err so that these also use the socket stream, so that there is 
(normally) only one communication channel, allowing us to fully process 
the out/err before finishing a command. This should also fix 
JDK-8131013. Note I kept the existing code to copy the RemoteAgent's 
stdout/stderr, just in case the RemoteAgent prints something there (for 
debugging, for example), even though this shouldn't be typically used.

-unfortunately, there are still some problems on Solaris, which I wasn't 
able to debug yet, so the test is excluded on Solaris.

-I added synchronization to JDIConnection, which should ensure proper 
access to the fields, and avoid the need to catch the NPE in JDIConnection.

-ReplToolTesting now converts the platform's line endings to '\n', to 
eliminate platform specific problems with line endings.

How does this look?

Thanks,
     Jan