kconfig: qconf: make debug links work again

The Qt5 conversion broke support for debug info links.

Restore the behaviour added by changeset
ab45d190 ("kconfig: create links in info window").

The original approach was to pass a pointer for a data struct
via an <a href>. That doesn't sound a good idea, as, if something
gets wrong, the app could crash. So, instead, pass the name of
the symbol, and validate such symbol at the hyperlink handling
logic.

Link: https://lore.kernel.org/lkml/20200628125421.12458086@coco.lan/


Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>