cleanup: remove copy contructors when the compiler is able to generate a satisfactory

default copy constructor; remove useless static_cast's; some misc cleanup.

Mainpage.dox

@@ -1,16 +1,16 @@
 o /** @mainpage Eigen
 
-<h3>If you see this page, then you have not properly generated the documentation.</h3>
+<h3>If you see this page, then you have not properly generated the documentation. Namely, you have run doxygen from the source directory, which is not appropriate for generating the documentation of Eigen.</h3>
 
-In order to generate the documentation for Eigen, follow these steps:
+In order to generate the documentation of Eigen, please follow these steps:
 <ul>
   <li>make sure you have the required software installed: cmake, doxygen, and a C++ compiler.
   <li>create a new directory, which we will call the "build directory", outside of the Eigen source directory.</li>
   <li>enter the build directory</li>
   <li>configure the project: <pre>cmake -DBUILD_DOC=ON /path/to/source/directory</pre></li>
-  <li>now generate the documentaion: <pre>make</pre> or, if you have two CPUs, <pre>make -j2</pre> Note that this will compile the examples, run them, and integrate their output into the documentation. This is why it can take some time.</li>
+  <li>now generate the documentaion: <pre>make</pre> or, if you have two CPUs, <pre>make -j2</pre> Note that this will compile the examples, run them, and integrate their output into the documentation, which can take some time.</li>
 </ul>
 
-You will now find the HTML documentation in the doc/html/ subdirectory of the build directory.
+After doing that, you will find the HTML documentation in the doc/html/ subdirectory of the build directory.
 
 */