Add setContentBorderAreaEnabled() which us used to
enable or disable an area. Used together with
registerContentBorderArea() this allows changing the
border area geometry and enabled status independently.
Add section to the QToolBar show/hide event handler
which calls setContentBorderAreaEnabled().
Make sure QToolBar and QToolBarLayout uses the same
identifier - the QToolBar object pointer.
Rename enableContentBorderArea -> setContentBorderEnabled.
The "ContentBorder" is now the entire unified toolbar
area while "ContentBorderArea"s are the sub-areas
covered by toolbars.
Change-Id: I339f381a50856e048ae40e7ffadd6a8a510c4994
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>