GLSL #version directive does not have to be at start of line

The #version directive detector of QOpenGLShaderProgram is using an
incorrect regular expression to detect the #version directive in the
preprocessed shader source code.

It is allowed to have whitespace before the #version.

Task-number: QTBUG-43240
Change-Id: If60670f49cb40148e5e7fbe6da6c798e8f636c3d
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>