[LyX/2.1.x] correct the error message for not supported automake version

[Stephan Witt]

commit f9d381c5c490a1e0ab28c8a337ce3948999f3522
Author: Stephan Witt <sw...@lyx.org>
Date:   Wed Jan 6 10:34:54 2016 +0100

    correct the error message for not supported automake version

diff --git a/autogen.sh b/autogen.sh
index 85652c0..b58c27b 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -20,7 +20,7 @@ case $automake_version in
        ;;
     *)
        echo "This automake version is not supported by LyX."
-       echo "LyX only supports automake 1.8 to 1.14."
+       echo "LyX only supports automake 1.8 to 1.15."
        exit 1
        ;;
 esac