Update stb_vorbis.

extras/stb_vorbis.c

-// Ogg Vorbis audio decoder - v1.19 - public domain
+// Ogg Vorbis audio decoder - v1.21 - public domain
 // http://nothings.org/stb_vorbis/
 //
 // Original version written by Sean Barrett in 2007.
@@ -31,9 +31,13 @@
 //    Phillip Bennefall  Rohit               Thiago Goulart
 //    github:manxorist   saga musix          github:infatum
 //    Timur Gagiev       Maxwell Koo         Peter Waller
-//    github:audinowho   Dougall Johnson
+//    github:audinowho   Dougall Johnson     David Reid
+//    github:Clownacy    Pedro J. Estebanez  Remi Verschelde
+//    AnthoFoxo
 //
 // Partial history:
+//    1.21    - 2021-07-02 - fix bug for files with no comments
+//    1.20    - 2020-07-11 - several small fixes
 //    1.19    - 2020-02-05 - warnings
 //    1.18    - 2020-02-02 - fix seek bugs; parse header comments; misc warnings etc.
 //    1.17    - 2019-07-08 - fix CVE-2019-13217..CVE-2019-13223 (by ForAllSecure)
@@ -577,7 +581,7 @@ enum STBVorbisError
    #if defined(_MSC_VER) || defined(__MINGW32__)
       #include <malloc.h>
    #endif
-   #if defined(__linux__) || defined(__linux) || defined(__EMSCRIPTEN__)
+   #if defined(__linux__) || defined(__linux) || defined(__EMSCRIPTEN__) || defined(__NEWLIB__)
       #include <alloca.h>
    #endif
 #else // STB_VORBIS_NO_CRT
@@ -963,7 +967,7 @@ static void *setup_temp_malloc(vorb *f, int sz)
 static void setup_temp_free(vorb *f, void *p, int sz)
 {
    if (f->alloc.alloc_buffer) {
-      f->temp_offset += (sz+3)&~3;
+      f->temp_offset += (sz+7)&~7;
       return;
    }
    free(p);
@@ -1602,7 +1606,8 @@ static uint32 get_bits(vorb *f, int n)
          f->valid_bits += 8;
       }
    }
-   if (f->valid_bits < 0) return 0;
+
+   assert(f->valid_bits >= n);
    z = f->acc & ((1 << n)-1);
    f->acc >>= n;
    f->valid_bits -= n;
@@ -3632,17 +3637,24 @@ static int start_decoder(vorb *f)
    //file vendor
    len = get32_packet(f);
    f->vendor = (char*)setup_malloc(f, sizeof(char) * (len+1));
+   if (f->vendor == NULL)                           return error(f, VORBIS_outofmem);
    for(i=0; i < len; ++i) {
       f->vendor[i] = get8_packet(f);
    }
    f->vendor[len] = (char)'\0';
    //user comments
    f->comment_list_length = get32_packet(f);
-   f->comment_list = (char**)setup_malloc(f, sizeof(char*) * (f->comment_list_length));
+   f->comment_list = NULL;
+   if (f->comment_list_length > 0)
+   {
+      f->comment_list = (char**) setup_malloc(f, sizeof(char*) * (f->comment_list_length));
+      if (f->comment_list == NULL)                  return error(f, VORBIS_outofmem);
+   }
 
    for(i=0; i < f->comment_list_length; ++i) {
       len = get32_packet(f);
       f->comment_list[i] = (char*)setup_malloc(f, sizeof(char) * (len+1));
+      if (f->comment_list[i] == NULL)               return error(f, VORBIS_outofmem);
 
       for(j=0; j < len; ++j) {
          f->comment_list[i][j] = get8_packet(f);
@@ -4255,7 +4267,7 @@ static void vorbis_init(stb_vorbis *p, const stb_vorbis_alloc *z)
    memset(p, 0, sizeof(*p)); // NULL out all malloc'd pointers to start
    if (z) {
       p->alloc = *z;
-      p->alloc.alloc_buffer_length_in_bytes = (p->alloc.alloc_buffer_length_in_bytes+3) & ~3;
+      p->alloc.alloc_buffer_length_in_bytes &= ~7;
       p->temp_offset = p->alloc.alloc_buffer_length_in_bytes;
    }
    p->eof = 0;