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/CMAKE_SYSTEM_PROGRAM_PATH.rst

@@ -0,0 +1,11 @@
+CMAKE_SYSTEM_PROGRAM_PATH
+-------------------------
+
+Path used for searching by FIND_PROGRAM().
+
+Specifies a path which will be used by FIND_PROGRAM().  FIND_PROGRAM()
+will check each of the contained directories for the existence of the
+program which is currently searched.  By default it contains the
+standard directories for the current system.  It is NOT intended to be
+modified by the project, use CMAKE_PROGRAM_PATH for this.  See also
+CMAKE_SYSTEM_PREFIX_PATH.