This avoids "*-caching variable does not exist" errors

Now, we get the URL directly. This is much simpler and much less
confusing. Also a few missing network protocols.

Improves seeking experience by sending less seek requests and actually allowing output to update between them.

indent comments screwed by copy-pasting

This patch needs more testing, I think.

Some instruction sets can't divide (e.g. ARM), but pretty much all of
them can shift bits.

dts spdif output was broken by the switch over to the new filter
API.

  * dtstofloat32 should only take control if there is _no_ spdif
    output requested otherwise the decoded stream ends up on the
    spdif device
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

A/52 spdif output was broken by the switch over to the new filter API.

  * a52tofloat32 should only take control if there is _no_ spdif
    output requested otherwise the decoded stream ends up on the spdif
    device

  * a52tospdif has to set a pts/dts value otherwise the frames get
    (wrongfully) discarded as too late because a wrong pts/dts value
    got evaluated by aout_OutputNextBuffer()
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

It just allows disabling their use.

 They now all mean that inline assembly (asm volatile (:::) for a specific
instruction set can be used.

(This is a really tiny fix but I'm used to use compile script).

This reverts commit ea4b6069.