Fixes the following warnings:
libavformat/hlsenc.c: In function 'hls_write_trailer':
libavformat/hlsenc.c:2364:17: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
uint8_t *buffer = NULL;
^~~~~~~
libavformat/hlsenc.c:2372:17: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || (hls->max_seg_size > 0);
^~~
libavformat/hlsenc.c:2379:13: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
int range_length = 0;
^~~
fc94e9704e