Doc: Added link to QtEndian page from Core Internals page.

-for better visibility

Change-Id: I6c81f1326e487dd50cf0bd275b359eea50bba435
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>