Debugger: Rework display length limitation systems

There are two values now, one to limit an entry in the L&E view
(default 100) and a hard upper limit (at 1 mio).

If displayed values are elided, the true length is shown in addition.

Change-Id: I180b70446c18e258c164e5af75b88d4c8b6c53f2
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/debugger/debuggeractions.h

@@ -148,6 +148,7 @@ enum DebuggerActionCode
     AutoDerefPointers,
     AlwaysAdjustLocalsColumnWidths,
     MaximalStringLength,
+    DisplayStringLimit,
 
     // Source List
     ListSourceFiles,