SHA1 checksum is no longer recommended by Apache release process

The Apache release process no longer recommends using SHA1 checksums
for artifacts http://www.apache.org/dev/release-signing.html#sha1.
The commit here removes generation of SHA1 for Ant distribution artifacts.

Furthermore, the checksum generation for artifacts that we upload to
Maven is also now removed, since the Nexus instance generates those dynamically
when the artifacts are uploaded to Nexus as stated at
http://www.apache.org/dev/publishing-maven-artifacts.html#prepare-release :
"You don't need artifacts for your checksum files (if you create any) since Nexus
 will create MD5 and SHA1 checksums on the fly anyway."

build.xml

@@ -942,24 +942,9 @@
     </copy>
   </target>
 
-  <macrodef name="checksums-mvn" description="only md5 and sha1 are needed for the maven directory structure">
-    <element name="resources" implicit="true"/>
-    <sequential>
-      <checksum algorithm="md5">
-        <resources/>
-      </checksum>
-      <checksum algorithm="sha1">
-        <resources/>
-      </checksum>
-    </sequential>
-  </macrodef>
-
   <macrodef name="checksums">
     <element name="resources" implicit="true"/>
     <sequential>
-      <checksum algorithm="sha1">
-        <resources/>
-      </checksum>
       <checksum fileext=".sha512" algorithm="sha-512">
         <resources/>
       </checksum>
@@ -1262,12 +1247,6 @@
         <include name="NOTICE.txt"/>
       </metainf>
     </jar>
-    <checksums-mvn>
-      <fileset dir="${java-repository.dir}" includes="**/*${project.version}.jar"/>
-      <fileset dir="${java-repository.dir}" includes="**/*${project.version}-sources.jar"/>
-      <fileset dir="${java-repository.dir}" includes="**/*${project.version}-javadoc.jar"/>
-      <fileset dir="${java-repository.dir}" includes="**/*${project.version}.pom"/>
-    </checksums-mvn>
 
     <zip destfile="${dist.base.manual}/${dist.name}-manual.zip">
       <zipfileset dir="${dist.name}/manual" prefix="${dist.name}"/>
@@ -1288,12 +1267,10 @@
     <checksums>
       <fileset dir="${dist.base.binaries}/">
         <exclude name="**/*.asc"/>
-        <exclude name="**/*.sha1"/>
         <exclude name="**/*.sha512"/>
       </fileset>
       <fileset dir="${dist.base.manual}/">
         <exclude name="**/*.asc"/>
-        <exclude name="**/*.sha1"/>
         <exclude name="**/*.sha512"/>
       </fileset>
     </checksums>
@@ -1336,7 +1313,6 @@
     <checksums>
       <fileset dir="${dist.base.source}/">
         <exclude name="**/*.asc"/>
-        <exclude name="**/*.sha1"/>
         <exclude name="**/*.sha512"/>
       </fileset>
     </checksums>