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>

doc/src/core.qdoc

@@ -127,5 +127,6 @@ Qt applications which support third-party plugins.
 \li \l{Qt Platform Abstraction}
 \li \l{Implementing Atomic Operations} - for new architectures
 \li \l{How to Create Qt Plugins}
+\li \l{Endian Conversion Functions} - functions for handling endianness from the QtEndian header
 \endlist
 */