Split it in several functions

After OpenDemux reads data using stream_Read(), it writes a '\0' to
the buffer after the newly-read data, but if the stream returned exactly
i_read_max bytes, this '\0' will end up just past the end of the allocated
psz_sdp array (see the call to realloc at the beginning of the loop).
Adjust the realloc call to allocate this one extra byte.
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

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