[ffvpx] Update ffvp9/ffvp8 to 3.4.2-release

Structure of code was slightly modified so that it should be no longer necessary to re-generate the config_*.h files, greatly simplifying the resync process in the future.

media/ffvpx/libavutil/utils.c

@@ -121,6 +121,29 @@ unsigned av_int_list_length_for_size(unsigned elsize,
     return i;
 }
 
+char *av_fourcc_make_string(char *buf, uint32_t fourcc)
+{
+    int i;
+    char *orig_buf = buf;
+    size_t buf_size = AV_FOURCC_MAX_STRING_SIZE;
+
+    for (i = 0; i < 4; i++) {
+        const int c = fourcc & 0xff;
+        const int print_chr = (c >= '0' && c <= '9') ||
+                              (c >= 'a' && c <= 'z') ||
+                              (c >= 'A' && c <= 'Z') ||
+                              (c && strchr(". -_", c));
+        const int len = snprintf(buf, buf_size, print_chr ? "%c" : "[%d]", c);
+        if (len < 0)
+            break;
+        buf += len;
+        buf_size = buf_size > len ? buf_size - len : 0;
+        fourcc >>= 8;
+    }
+
+    return orig_buf;
+}
+
 AVRational av_get_time_base_q(void)
 {
     return (AVRational){1, AV_TIME_BASE};
@@ -129,7 +152,7 @@ AVRational av_get_time_base_q(void)
 void av_assert0_fpu(void) {
 #if HAVE_MMX_INLINE
     uint16_t state[14];
-     __asm volatile (
+     __asm__ volatile (
         "fstenv %0 \n\t"
         : "+m" (state)
         :