V8DebuggerClient: Enable breakpoints on Exceptions

Previously break on exceptions was always enabled. Now, the user
can add a breakpoint on Javascript Exceptions from the breakpoint
window in the debugger.

Change-Id: Ia9ee813d2fccf89b607fe1dcbad47b4084155a48
Reviewed-on: http://codereview.qt-project.org/6348
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

src/plugins/debugger/breakpoint.cpp

@@ -277,6 +277,7 @@ QString BreakpointParameters::toString() const
     case BreakpointAtExec:
     //case BreakpointAtVFork:
     case BreakpointAtSysCall:
+    case BreakpointAtJavaScriptThrow:
     case UnknownType:
         break;
     }