[8u20] RFR: 8038027: DTDBuilder should be run in headless mode

[David DeHaven]

And now actually including build-dev...

Please review this slightly different backport of JDK-8038027 to 8u.

-DrD-

> 
> Please review my trivial backport of JDK-8038027. The actual change is identical to 9, the difference is the surrounding $(JAVA) is $(JAVA_SMALL) in JDK 9.
> 
> JBS Issue:
> https://bugs.openjdk.java.net/browse/JDK-8038027
> 
> JDK 9 changeset:
> http://hg.openjdk.java.net/jdk9/dev/jdk/rev/0eab6c63201d
> 
> JDK 9 review:
> http://mail.openjdk.java.net/pipermail/build-dev/2014-March/012182.html
> 
> 8u patch:
> --- cut here ---
> diff --git a/make/Tools.gmk b/make/Tools.gmk
> --- a/make/Tools.gmk
> +++ b/make/Tools.gmk
> @@ -80,6 +80,7 @@
>     build.tools.generatecharacter.CharacterName
> 
> TOOL_DTDBUILDER = $(JAVA) -Ddtd_home=$(JDK_TOPDIR)/make/data/dtdbuilder \
> +    -Djava.awt.headless=true \
>     -cp $(JDK_OUTPUTDIR)/btclasses build.tools.dtdbuilder.DTDBuilder
> 
> TOOL_GENERATEBREAKITERATORDATA = $(JAVA) \
> --- cut here ---
> 
> -DrD-
>