configure: bump year

Happy new year!

(cherry picked from commit bddf31ba75)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

configure

@@ -6144,7 +6144,7 @@ cat > $TMPH <<EOF
 #define FFMPEG_CONFIG_H
 #define FFMPEG_CONFIGURATION "$(c_escape $FFMPEG_CONFIGURATION)"
 #define FFMPEG_LICENSE "$(c_escape $license)"
-#define CONFIG_THIS_YEAR 2017
+#define CONFIG_THIS_YEAR 2018
 #define FFMPEG_DATADIR "$(eval c_escape $datadir)"
 #define AVCONV_DATADIR "$(eval c_escape $datadir)"
 #define CC_IDENT "$(c_escape ${cc_ident:-Unknown compiler})"