Convert builtin help to reStructuredText source files

Run the convert-help.bash script to convert documentation:

 ./convert-help.bash "/path/to/CMake-build/bin"

Then remove it.

Help/variable/MSVC_VERSION.rst

@@ -0,0 +1,17 @@
+MSVC_VERSION
+------------
+
+The version of Microsoft Visual C/C++ being used if any.
+
+Known version numbers are:
+
+::
+
+  1200 = VS  6.0
+  1300 = VS  7.0
+  1310 = VS  7.1
+  1400 = VS  8.0
+  1500 = VS  9.0
+  1600 = VS 10.0
+  1700 = VS 11.0
+  1800 = VS 12.0