[PATCH] doc: Add config check for doxygen 1.8.0+.

[Bill Spitzak]

Thanks! You know I tried searching for "version" in the autotools 
documents, but did not find this. That documentation is pretty incomplete.

Note that as far as I can tell the only feature we are using is the 
tildes for code markup, and that is being questioned right now.

On 12/02/2014 09:48 PM, Jon A. Cruz wrote:
> Add a config time check for a new enough (1.8.0+) version of doxygen.
>
> Signed-off-by: Jon A. Cruz <jonc at osg.samsung.com>
> ---
>   configure.ac | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/configure.ac b/configure.ac
> index 6f8220b..317cdae 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -109,6 +109,14 @@ if test "x$enable_documentation" = "xyes"; then
>   		AC_MSG_ERROR([Documentation build requested but doxygen not found. Install doxygen or disable the documentation using --disable-documentation])
>   	fi
>
> +	AC_MSG_CHECKING([for compatible doxygen version])
> +	doxygen_version=`$DOXYGEN --version`
> +	AS_VERSION_COMPARE([$doxygen_version], [1.8.0],
> +	                   [AC_MSG_RESULT([no])
> +	                    AC_MSG_ERROR([Doxygen $doxygen_version too old. Doxygen 1.8+ required for documentation build. Install required doxygen version or disable the documentation using --disable-documentation])],
> +	                   [AC_MSG_RESULT([yes])],
> +	                   [AC_MSG_RESULT([yes])])
> +
>   	AC_PATH_PROG(XMLTO, xmlto)
>
>   	if test "x$XMLTO" = "x"; then
>