Fail early when creating QOpenGLVertexArrayObject

There is a significant performance regression with using
QOpenGLVertexArrayObject::Binder on platforms not supporting VAOs. This
is because of the function resolving/initialization in create which is
called once pr bind if d->vao == 0.

Change-Id: I74e77f50921116c306247dc371c68b287a2e22d7
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
tst_QString: Use a non-empty string for lastIndexOfInvalidRegex

Testing using an empty string doesn't ensure that the regexp
gets validated. The function may return earlier thus making
the test useless. This patch adds a text to search in so that
no early optimization avoids the regexp validation part

Change-Id: If24b77385dde44a922d43e5ae1d7a5393d24f640
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
QString:add (last)indexOf overload with QRegularExpressionMatch output

This patch adds indexOf and lastIndexOf with QRegularExpressionMatch
output overloads to QString. This allows to get the match corresponding
to the index returned.

[ChangeLog][QtCore][QString] Added support for retrieving the
QRegularExpressionMatch to indexOf and lastIndexOf.

Change-Id: Ia0ae2d3ff78864c7053ffa397874aca1d2b1c35c
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>