vf_hqdn3d: Don't declare the loop variable within the for loop

This C99 feature is generally not used in the libav codebase,
since it breaks building with some fringe compilers (GCC 2.95,
MSVC).
Signed-off-by: Martin Storsjö <martin@martin.st>

libavfilter/vf_hqdn3d.c

@@ -295,6 +295,7 @@ static int query_formats(AVFilterContext *ctx)
 static int config_input(AVFilterLink *inlink)
 {
     HQDN3DContext *hqdn3d = inlink->dst->priv;
+    int i;
 
     hqdn3d->hsub = av_pix_fmt_descriptors[inlink->format].log2_chroma_w;
     hqdn3d->vsub = av_pix_fmt_descriptors[inlink->format].log2_chroma_h;
@@ -304,7 +305,7 @@ static int config_input(AVFilterLink *inlink)
     if (!hqdn3d->line)
         return AVERROR(ENOMEM);
 
-    for (int i=0; i<4; i++) {
+    for (i = 0; i < 4; i++) {
         hqdn3d->coefs[i] = precalc_coefs(hqdn3d->strength[i], hqdn3d->depth);
         if (!hqdn3d->coefs[i])
             return AVERROR(ENOMEM);