Fix usage of C99

It's 2020, way too early for that, let's stick to C89 for now.

gst/rtpmanager/rtptwcc.c

@@ -293,16 +293,18 @@ rtp_twcc_write_status_vector_chunk (ChunkBitWriter * writer, RecvPacket * pkt)
   if (pkt->missing_run > 0) {
     guint available = chunk_bit_writer_get_available_slots (writer);
     guint total = chunk_bit_writer_get_total_slots (writer);
+    guint i;
+
     if (pkt->missing_run > (available + total)) {
       /* here it is better to finish up the current status-chunk and then
          go for run-length */
-      for (guint i = 0; i < available; i++) {
+      for (i = 0; i < available; i++) {
         chunk_bit_writer_write (writer, RTP_TWCC_PACKET_STATUS_NOT_RECV);
       }
       rtp_twcc_write_run_length_chunk (writer->packet_chunks,
           RTP_TWCC_PACKET_STATUS_NOT_RECV, pkt->missing_run - available);
     } else {
-      for (guint i = 0; i < pkt->missing_run; i++) {
+      for (i = 0; i < pkt->missing_run; i++) {
         chunk_bit_writer_write (writer, RTP_TWCC_PACKET_STATUS_NOT_RECV);
       }
     }
@@ -696,13 +698,14 @@ _parse_run_length_chunk (GstBitReader * reader, GArray * twcc_packets,
 {
   guint run_length;
   guint8 status_code;
+  guint i;
 
   gst_bit_reader_get_bits_uint8 (reader, &status_code, 2);
 
   run_length = *(guint16 *) reader->data & ~0xE0;       /* mask out the 3 last bits */
   run_length = MIN (remaining_packets, GST_READ_UINT16_BE (&run_length));
 
-  for (guint i = 0; i < run_length; i++) {
+  for (i = 0; i < run_length; i++) {
     _add_twcc_packet (twcc_packets, seqnum_offset + i, status_code);
   }
 
@@ -715,12 +718,13 @@ _parse_status_vector_chunk (GstBitReader * reader, GArray * twcc_packets,
 {
   guint8 symbol_size;
   guint num_bits;
+  guint i;
 
   gst_bit_reader_get_bits_uint8 (reader, &symbol_size, 1);
   symbol_size += 1;
   num_bits = MIN (remaining_packets, 14 / symbol_size);
 
-  for (guint i = 0; i < num_bits; i++) {
+  for (i = 0; i < num_bits; i++) {
     guint8 status_code;
     if (gst_bit_reader_get_bits_uint8 (reader, &status_code, symbol_size))
       _add_twcc_packet (twcc_packets, seqnum_offset + i, status_code);

gst/videocrop/gstvideocrop.c

@@ -333,16 +333,18 @@ gst_video_crop_transform_planar (GstVideoCrop * vcrop,
 {
   const GstVideoFormatInfo *format_info;
   gint crop_top, crop_left;
+  guint p;
 
   format_info = in_frame->info.finfo;
   crop_left = vcrop->crop_left + x;
   crop_top = vcrop->crop_top + y;
 
-  for (guint p = 0; p < GST_VIDEO_FRAME_N_PLANES (in_frame); ++p) {
+  for (p = 0; p < GST_VIDEO_FRAME_N_PLANES (in_frame); ++p) {
     guint8 *plane_in, *plane_out;
     guint sub_w_factor, sub_h_factor;
     guint subsampled_crop_left, subsampled_crop_top;
     guint copy_width;
+    gint i;
 
     /* plane */
     plane_in = GST_VIDEO_FRAME_PLANE_DATA (in_frame, p);
@@ -366,7 +368,7 @@ gst_video_crop_transform_planar (GstVideoCrop * vcrop,
         subsampled_crop_left);
     copy_width = (guint) GST_VIDEO_FRAME_COMP_WIDTH (out_frame, p);
 
-    for (gint i = 0; i < GST_VIDEO_FRAME_COMP_HEIGHT (out_frame, p); ++i) {
+    for (i = 0; i < GST_VIDEO_FRAME_COMP_HEIGHT (out_frame, p); ++i) {
       memcpy (plane_out, plane_in, copy_width);
       plane_in += GST_VIDEO_FRAME_PLANE_STRIDE (in_frame, p);
       plane_out += GST_VIDEO_FRAME_PLANE_STRIDE (out_frame, p);

tests/check/elements/rtpbin.c

@@ -939,7 +939,9 @@ _pad_added (G_GNUC_UNUSED GstElement * rtpbin, GstPad * pad, GstHarness * h)
 
 GST_START_TEST (test_quick_shutdown)
 {
-  for (guint r = 0; r < 1000; r++) {
+  guint r;
+
+  for (r = 0; r < 1000; r++) {
     guint i;
     GstHarness *h = gst_harness_new_with_padnames ("rtpbin",
         "recv_rtp_sink_0", NULL);

tests/check/elements/rtpsession.c

@@ -3568,7 +3568,9 @@ GST_START_TEST (test_twcc_send_and_recv)
 
   for (frame = 0; frame < num_frames; frame++) {
     GstBuffer *buf;
-    for (guint slice = 0; slice < num_slices; slice++) {
+    guint slice;
+
+    for (slice = 0; slice < num_slices; slice++) {
       GstFlowReturn res;
       guint seq = frame * num_slices + slice;