avcodec/internal: move FF_QSCALE_TYPE defines from avcodec.h

Their use in the public header is deprecated and will be removed, but
they are still needed by some codecs at least as long as qscale related
deprecated fields in the AVFrame struct remain in the tree.

libavcodec/internal.h

@@ -76,6 +76,13 @@
 #define FF_DEFAULT_QUANT_BIAS 999999
 #endif
 
+#if !FF_API_QSCALE_TYPE
+#define FF_QSCALE_TYPE_MPEG1 0
+#define FF_QSCALE_TYPE_MPEG2 1
+#define FF_QSCALE_TYPE_H264  2
+#define FF_QSCALE_TYPE_VP56  3
+#endif
+
 #define FF_SANE_NB_CHANNELS 64U
 
 #define FF_SIGNBIT(x) ((x) >> CHAR_BIT * sizeof(x) - 1)