all: unmark experimental features

It's been some time now we've had those features, so unmark them
being experimental.

It does not mean everything is perfect, but may gather some more
testing of those features.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 This is NOT the official version of dialog.  This version has been

 significantly modified from the original.  It is for use by the Linux

 kernel configuration script.  Please do not bother Savio Lam with 

 questions about this program.