CTR: no code change, fix an issue with svn maintenance

Merged revision r1561636 from tomcat/tc7.0.x/trunk:
Remove svn:mime-type property from *.dtd files.
The value was application/xml-dtd.

A mime-type is not needed on these source files, and it is inconvenient:
application/* mime types make SVN to treat the files as binary ones.
It did not show diffs on them.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1561638 13f79535-47bb-0310-9956-ffa450edef68
proposal

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1561642 13f79535-47bb-0310-9956-ffa450edef68
Vote.


git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1561644 13f79535-47bb-0310-9956-ffa450edef68