Core: Fix MSVC compiler warning about strdup

Fix

 warning: C4996: 'strdup': The POSIX name for this item is deprecated. Instead, use the ISO C++ conformant name: _strdup.

 By just using qstrdup.

Change-Id: I40664b6ed763b27951d983ec13dcc638270a1beb
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/coreplugin/id.cpp

@@ -107,7 +107,7 @@ static int theId(const char *str)
         if (lastUid == 0)
             stringFromId.append(QByteArray());
         res = ++lastUid;
-        sh.str = strdup(sh.str);
+        sh.str = qstrdup(sh.str);
         idFromString[sh] = res;
         stringFromId.append(QByteArray::fromRawData(sh.str, sh.n));
     }