Drop ant-1.7 from project, advance Ant to 1.8.2

Ant 1.8.2 has the API (namely,
CompilerAdapterExtension#getSupportedFileExtensions) which will allow to fix a
critical bug in <withKotlin/> task (see KT-7870)

build.xml

@@ -577,7 +577,7 @@
             <classpath>
                 <file file="${bootstrap.runtime}"/>
                 <file file="${bootstrap.reflect}"/>
-                <pathelement location="${dependencies.dir}/ant-1.7/lib/ant.jar"/>
+                <pathelement location="${dependencies.dir}/ant-1.8/lib/ant.jar"/>
                 <pathelement location="${kotlin-home}/lib/kotlin-preloader.jar"/>
             </classpath>
         </javac2>