The main window may be asked to update its content prior to VLCFSPanel being fully initialized

Some filters and outputs rely on the samples count (which was correct),
others on the bytes size (which was not), accounting for why decoding
failed only in some combinations.

That is recommended by MSDN. Also, do not use 0 for NULL.

It is not needed anymore since ce652138 , parsing will
stop at first unrecognized character (like \r or \n)

This affects: .opus, .ogx, .wtv, .rec, .vro, .tod and .mks

This avoids grey or transparent flashes on start

Note that this commit will break some stuff for non-embedded cases, for now.

refs #6814

Quoting the reporter:
| According to include/vlc_access.h, access_t.psz_location is "URL with
| the scheme stripped". But in http module, schema stays there after
| 302 redirection. That may cause httplive module try to access URL like
| "http://http://host/path".
Pointed-out-by: bbcallen <bbcallen@gmail.com>

If a certificate does not validate, the user will be given the option
to accept it manually. GnuTLS will then store the certificate in its
known hosts database.

This will be used for fine-grained GnuTLS stored public keys,
i.e. SSH-like authentication on first use.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

Close #7529

Keeping the credentials container saves some times, as we do not need
to load and parse all of the 100+ Certificate Authorities again.
In the future, it will also avoid reloading the stored public keys
(i.e. security exceptions), or asking for user confirmation again.

Given how the HTTP access is written, the credentials are now preserved
upon seeking. Unfortunately, they are not recycled across redirections
as access_t.p_sys gets destroyed internally. This also does not work
across multiple inputs - support from the instance or input manager
would be required.

The TLS plugin now supports reusing the same set of credentials for
multiple sessions also on the client side.

Support for custom certificates will be better addressed with the
stored public key support in the GnuTLS library (in latter commit).

Support for private keys on client side was practically useless.