merge declaration and initial assignement

Replace macro with static inline and use bounds checking

While useful, this is not permitted by the standard specification.
This patch will waste a little bit of memory in affected allocations...

This reverts commit 5086a9ed.

When we moved the code to use the legacy method *or* the new method,
we lost the functionality that actually initialized the memory allocated
for the entire subpicture region (including the part where captions
weren't being rendered.

This was most obvious when regression testing on OSX, where it
resulted in old captions continuing to appear on screen even
after being cleared, or garbage in the render buffer.

Add a line that effectively zeros out the buffer prior to use.
Signed-off-by: Rafaël Carré <funman@videolan.org>

swprintf is not the standard function you are looking for

Since it never built, it was never needed on any platform

'libvpx' decoder doesn't exist anymore but we continue to disable it anyway
for people building and older version

This would need more testing and close look

This needs testing

This would deserve a second look, though

This does not support hot plug and unplug of devices.

Also, it prevented selecting a device not in the choices list due to
checks in the variables subsystem. (At least with ALSA, not all valid
devices are included in the suggestions.)