RFR: 8038027: DTDBuilder should be run in headless mode

[David DeHaven]

>> Please review a simple fix for a cosmetic issue:
>> https://bugs.openjdk.java.net/browse/JDK-8038027
>> 
>> Proposed fix:
>> diff --git a/make/Tools.gmk b/make/Tools.gmk
>> --- a/make/Tools.gmk
>> +++ b/make/Tools.gmk
>> @@ -71,6 +71,7 @@
>>     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) \
>> 
>> 
>> Test run showed no change in build results.
>> 
>> Need a sponsor to push, any volunteers?
> 
> Looks good to me.
> 
> I can sponsor this fix.

Thanks. I'll email a proper patch since cut and paste butchered this one...

-DrD-