Debugger: Avoid reserving huge strings

Fixes: QTCREATORBUG-26416
Change-Id: I3728a98f0d16f43817d46e5404bd0b65bfd1b9c0
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/debuggerprotocol.cpp

@@ -200,7 +200,7 @@ QString DebuggerOutputParser::readCString()
 
     ++from; // Skip initial quote.
     QString result;
-    result.reserve(to - from);
+    result.reserve(30);
     while (from < to) {
         if (*from == '"') {
             ++from;