Limit key frame quantizer for forced key frames.

Where a key frame occurs because of a minimum interval
selected by the user, then these forced key frames ideally need
to be more closely matched in quality to the surrounding frame.

Change-Id: Ia55b1f047e77dc7fbd78379c45869554f25b3df7
diff --git a/vp8/encoder/onyx_int.h b/vp8/encoder/onyx_int.h
index 6bffd98..6b07e2f 100644
--- a/vp8/encoder/onyx_int.h
+++ b/vp8/encoder/onyx_int.h
@@ -317,7 +317,8 @@
 
     unsigned int frames_since_key;
     unsigned int key_frame_frequency;
-    unsigned int next_key;
+    unsigned int this_key_frame_forced;
+    unsigned int next_key_frame_forced;
 
     unsigned int mode_check_freq[MAX_MODES];
     unsigned int mode_test_hit_counts[MAX_MODES];