Call svt_av1_get_version() for v0.9.0 or later

The svt_av1_get_version() function was added in SVT-AV1 v0.9.0. Have
avifCodecVersionSvt() call svt_av1_get_version() for v0.9.0 or later.

Add an initial "v" to SVT_FULL_VERSION (now only used for versions older
than v0.9.0) to match the format of the string that
svt_av1_get_version() returns.

src/codec_svt.c

diff --git a/src/codec_svt.c b/src/codec_svt.c
index b1a6bbf..f7173ad 100644
--- a/src/codec_svt.c
+++ b/src/codec_svt.c
@@ -25,9 +25,11 @@
 // clang-format on
 #endif
 
+#if !SVT_AV1_CHECK_VERSION(0, 9, 0)
 #define STR_HELPER(x) #x
 #define STR(x) STR_HELPER(x)
-#define SVT_FULL_VERSION STR(SVT_AV1_VERSION_MAJOR) "." STR(SVT_AV1_VERSION_MINOR) "." STR(SVT_AV1_VERSION_PATCHLEVEL)
+#define SVT_FULL_VERSION "v" STR(SVT_AV1_VERSION_MAJOR) "." STR(SVT_AV1_VERSION_MINOR) "." STR(SVT_AV1_VERSION_PATCHLEVEL)
+#endif
 
 typedef struct avifCodecInternal
 {
@@ -219,7 +221,11 @@
 
 const char * avifCodecVersionSvt(void)
 {
+#if SVT_AV1_CHECK_VERSION(0, 9, 0)
+    return svt_av1_get_version();
+#else
     return SVT_FULL_VERSION;
+#endif
 }
 
 static void svtCodecDestroyInternal(avifCodec * codec)