Added global-property to DTD.

Removed DTD from XML file until fix of ConfigurationLoader

build.xml

@@ -639,7 +639,8 @@
     <target name="validate.xml"
             depends="require.xerces"
             description="Validates checkstyle XML file">
-        <xmlvalidate file="docs/checkstyle_checks.xml"/>
+        <xmlvalidate file="docs/checkstyle_checks.xml">
+        </xmlvalidate>
     </target>
 
 </project>

docs/checkstyle_checks.xml

@@ -1,8 +1,11 @@
 <?xml version="1.0"?>
+<!-- TODO: fix the loader to not validate the file 
 <!DOCTYPE configuration SYSTEM "configuration.dtd">
-
+ -->
 <configuration>
 
+    <global-property name="tabWidth" value="4"/>
+
     <check classname="com.puppycrawl.tools.checkstyle.checks.AvoidStarImport"/>
 
     <check classname="com.puppycrawl.tools.checkstyle.checks.ConstantNameCheck"/>

docs/configuration.dtd

@@ -1,11 +1,15 @@
 <!--
  DTD for a checkstyle configuration.
  -->
-<!ELEMENT configuration (check*)>
+<!ELEMENT configuration (global-property*, check*)>
+<!ELEMENT global-property EMPTY>
 <!ELEMENT check (tokens?, set-property?)>
 <!ELEMENT tokens (#PCDATA)>
 <!ELEMENT set-property EMPTY>
 
+<!ATTLIST global-property name CDATA #REQUIRED
+                          value CDATA #REQUIRED
+>
 <!ATTLIST check classname CDATA #REQUIRED>
 <!ATTLIST set-property name CDATA #REQUIRED
                        value CDATA #REQUIRED