bytestream: Make get_bytes_left compatible with overread

bytestream2_get_bytes_left returns an unsigned int; as a result,
it returns big positive numbers if an overread already happened,
making it unsuitable for scenarios where one wants to allow this
in a controlled way (because the buffer is actually padded so that
no segfaults can happen). So change it to return an ordinary int.

Also, bytestream2_get_bytes_left_p has been modified in the same way.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/bytestream.h

@@ -151,12 +151,12 @@ static av_always_inline void bytestream2_init_writer(PutByteContext *p,
     p->eof          = 0;
 }
 
-static av_always_inline unsigned int bytestream2_get_bytes_left(GetByteContext *g)
+static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
 {
     return g->buffer_end - g->buffer;
 }
 
-static av_always_inline unsigned int bytestream2_get_bytes_left_p(PutByteContext *p)
+static av_always_inline int bytestream2_get_bytes_left_p(PutByteContext *p)
 {
     return p->buffer_end - p->buffer;
 }