Doc: Qt Concurrent: Link to essential usage information

Functions under the QtConcurrent namespace used to be documented
as header files, using the \headerfile command. These documents
have been since converted to standard pages using the \page
command, and the reference documentation for these functions
now live in the namespace page only.

However, the former pages contain useful usage information and
code snippets, but they've not been linked to from anywhere.

This change links to these pages from the module landing page,
as well as from the function reference doc.

Change-Id: Ia750d72d12503cec96ee2c9e202dd561e548cb24
Task-number: QTBUG-28977
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@theqtcompany.com>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>

0 files changed, 0 insertions, 0 deletions