RFR: 8185752: update javadoc options in make/Docs.gmk

[Tim Bell]

Hi Jon:

> Please review the following small fix to update the javadoc options in
> make/Docs.gmk.
>
> JBS: https://bugs.openjdk.java.net/browse/JDK-8185752
>
> No webrev: here is the patch, to add the -docencoding option,
> and to remove the -XDignore.symbol.file option


Looks good to me.

Tim

> -- Jon
>
>
> $ hg diff
> diff -r 536b81db8075 make/Docs.gmk
> --- a/make/Docs.gmk    Fri Jul 28 02:34:33 2017 +0000
> +++ b/make/Docs.gmk    Wed Aug 02 15:00:09 2017 -0700
> @@ -101,9 +101,9 @@
>   JAVADOC_DISABLED_DOCLINT := accessibility html missing syntax reference
>
>   # The initial set of options for javadoc
> -JAVADOC_OPTIONS := -XDignore.symbol.file=true -use -keywords
> -notimestamp \
> -    -serialwarn -encoding ISO-8859-1 -breakiterator -splitIndex
> --system none \
> -    -html5 -javafx --expand-requires transitive
> +JAVADOC_OPTIONS := -use -keywords -notimestamp \
> +    -serialwarn -encoding ISO-8859-1 -docencoding UTF-8 -breakiterator \
> +    -splitIndex --system none -html5 -javafx --expand-requires transitive
>
>   # Should we add DRAFT stamps to the generated javadoc?
>   ifeq ($(VERSION_IS_GA), true)
>