Add git commands for apr checkout to INSTALL

Submitted by: Vladimír Chlup <vchlup redhat.com>
Github: closes #437


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1923812 13f79535-47bb-0310-9956-ffa450edef68

INSTALL

@@ -80,6 +80,10 @@
 
     Check out APR trunk in srclib/apr with the following command:
 
+    git clone https://github.com/apache/apr.git srclib/apr
+
+    or alternatively using svn:
+
     svn co http://svn.apache.org/repos/asf/apr/apr/trunk srclib/apr
 
     buildconf will find it automatically.  Use the --with-included-apr
@@ -90,6 +94,11 @@
     Check out the current branches as srclib/apr and srclib/apr-util with
     the following commands:
 
+    git clone -b 1.7.x https://github.com/apache/apr.git srclib/apr
+    git clone -b 1.6.x https://github.com/apache/apr-util.git srclib/apr-util
+
+    or alternatively using svn:
+
     svn co http://svn.apache.org/repos/asf/apr/apr/branches/1.7.x srclib/apr
     svn co http://svn.apache.org/repos/asf/apr/apr-util/branches/1.6.x srclib/apr-util