MT#61856 recording-daemon: update const qualifiers

Don't use const in:
- output_avio_mem_write()
- output_avio_write()

`avio_alloc_context()` of avio.h lib wants buf
to be non-constant.

Also it's the only usage of locally defined funcs,
moreover:
- output_avio_write() has fwrite() that protects buf with const
- output_avio_mem_write() casts given buf to `const char*`

Fixes:

output.c: In function ‘output_config’:
output.c:405:39: warning: passing argument 6 of ‘avio_alloc_context’ from incompatible pointer type [-Wincompatible-pointer-types]
  405 |                                 NULL, output_avio_write, output_avio_seek);
      |                                       ^~~~~~~~~~~~~~~~~
      |                                       |
      |                                       int (*)(void *, const uint8_t *, int) {aka int (*)(void *, const unsigned char *, int)}
In file included from /usr/include/x86_64-linux-gnu/libavformat/avformat.h:316,
                 from types.h:9,
                 from output.h:4,
                 from output.c:1:
/usr/include/x86_64-linux-gnu/libavformat/avio.h:468:25: note: expected ‘int (*)(void *, uint8_t *, int)’
                          {aka ‘int (*)(void *, unsigned char *, int)’} but argument is of type
                          ‘int (*)(void *, const uint8_t *, int)’ {aka ‘int (*)(void *, const unsigned char *, int)’}
  468 |                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
      |                   ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

int (*)(void *, const uint8_t *, int) {aka int (*)(void *, const unsigned char *, int)}
int (*)(void *, const uint8_t *, int)

output.c:409:39: warning: passing argument 6 of ‘avio_alloc_context’ from incompatible pointer type [-Wincompatible-pointer-types]
  409 |                                 NULL, output_avio_mem_write, output_avio_mem_seek);
      |                                       ^~~~~~~~~~~~~~~~~~~~~
      |                                       |
      |                                       int (*)(void *, const uint8_t *, int) {aka int (*)(void *, const unsigned char *, int)}
In file included from /usr/include/x86_64-linux-gnu/libavformat/avformat.h:316,
                 from types.h:9,
                 from output.h:4,
                 from output.c:1:
/usr/include/x86_64-linux-gnu/libavformat/avio.h:468:25: note: expected ‘int (*)(void *, uint8_t *, int)’
                          {aka ‘int (*)(void *, unsigned char *, int)’} but argument is of type
                          ‘int (*)(void *, const uint8_t *, int)’ {aka ‘int (*)(void *, const unsigned char *, int)’}
  468 |                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
      |                   ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: Leaving directory '/home/donat/git/sipwise/rtpengine/recording-daemon'

Change-Id: Ied4936fe24d55c241a3f72550e643368a014c181

recording-daemon/output.c

@@ -317,7 +317,11 @@ output_t *output_new_ext(metafile_t *mf, const char *type, const char *kind, con
 	return ret;
 }
 
+#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(61, 0, 0)
 int output_avio_write(void *opaque, const uint8_t *buf, int buf_size) {
+#else
+int output_avio_write(void *opaque, uint8_t *buf, int buf_size) {
+#endif
 	output_t *o = opaque;
 	ssize_t written = fwrite(buf, buf_size, 1, o->fp);
 	if (written == 1)
@@ -331,7 +335,11 @@ int64_t output_avio_seek(void *opaque, int64_t offset, int whence) {
 	return ftell(o->fp);
 }
 
+#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(61, 0, 0)
 int output_avio_mem_write(void *opaque, const uint8_t *buf, int buf_size) {
+#else
+int output_avio_mem_write(void *opaque, uint8_t *buf, int buf_size) {
+#endif
 	output_t *o = opaque;
 	g_string_overwrite_len(o->membuf, o->mempos, (const char *) buf, buf_size);
 	o->mempos += buf_size;