Merge pull request #7855 from jppelteret/sd-doc_01

Add SymEngine to the readme file in the documentation

doc/readme.html

@@ -604,6 +604,16 @@ <h4>Optional interfaces to other software packages</h4>
                     <code>-DSUNDIALS_DIR=/path/to/sundials</code> to the deal.II CMake call.
                 </p>
             </dd>
+
+            <dt><a name="SymEngine"/>
+                <a href="https://symengine.github.io/" target="_top">SymEngine</a></dt>
+            <dd>
+                <p>
+                    <a href="https://github.com/symengine/symengine/" target="_top">SymEngine</a> is a symbolic manipulation package, implementing the building blocks of a computer algebra system (CAS) similar to <a href="https://www.sympy.org/en/index.html" target="_top">SymPy</a>. In particular, it can be used for symbolic differentiation. For using
+                    <a href="https://symengine.github.io/" target="_top">SymEngine</a> with deal.II, version 0.4 or newer is required. To use a self compiled version, pass
+                    <code>-DSYMENGINE_DIR=/path/to/symengine</code> to the deal.II CMake call.
+                </p>
+            </dd>
 
             <dt><a name="tbb"></a><a href="http://www.threadingbuildingblocks.org/"
 	     target="_top">Threading Building Blocks (TBB)</a></dt>