Introduce first_avfilter and use that, together with AVFilter.next,

for registering and finding filters, rather than use the struct
AVFilterList, which is removed.

Simplify the filter registration management code.

Originally committed as revision 20387 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavfilter/avfilter.c

@@ -28,13 +28,6 @@ unsigned avfilter_version(void) {
     return LIBAVFILTER_VERSION_INT;
 }
 
-/** list of registered filters */
-static struct FilterList
-{
-    AVFilter *filter;
-    struct FilterList *next;
-} *filters = NULL;
-
 /** helper macros to get the in/out pad on the dst/src filter */
 #define link_dpad(link)     link->dst-> input_pads[link->dstpad]
 #define link_spad(link)     link->src->output_pads[link->srcpad]
@@ -327,34 +320,33 @@ void avfilter_draw_slice(AVFilterLink *link, int y, int h)
     draw_slice(link, y, h);
 }
 
+AVFilter *first_avfilter = NULL;
+
 AVFilter *avfilter_get_by_name(const char *name)
 {
-    struct FilterList *filt;
+    AVFilter *filter;
 
-    for(filt = filters; filt; filt = filt->next)
-        if(!strcmp(filt->filter->name, name))
-            return filt->filter;
+    for (filter = first_avfilter; filter; filter = filter->next)
+        if (!strcmp(filter->name, name))
+            return filter;
 
     return NULL;
 }
 
 void avfilter_register(AVFilter *filter)
 {
-    struct FilterList *newfilt = av_malloc(sizeof(struct FilterList));
+    AVFilter **p;
+    p = &first_avfilter;
+    while (*p)
+        p = &(*p)->next;
 
-    newfilt->filter = filter;
-    newfilt->next   = filters;
-    filters         = newfilt;
+    *p = filter;
+    filter->next = NULL;
 }
 
 void avfilter_uninit(void)
 {
-    struct FilterList *tmp;
-
-    for(; filters; filters = tmp) {
-        tmp = filters->next;
-        av_free(filters);
-    }
+    first_avfilter = NULL;
 }
 
 static int pad_count(const AVFilterPad *pads)