Fix a warning found by MSVC2010_64

Change-Id: Ie9ae9a8c8bff87a610606e3a6075987a08ed0644
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/coreplugin/id.cpp

@@ -73,7 +73,7 @@ public:
         : n(length), str(s)
     {
         if (!n)
-            length = n = strlen(s);
+            length = n = static_cast<int>(strlen(s));
         h = 0;
         while (length--) {
             h = (h << 4) + *s++;