Help: Fix installation of the Qt qch file.

The file was changed to have the version in its name in
commit 111bb67c (Help: Use a more-appropriate qthelp namespace and
file name., 2014-04-10).

Utilities/Sphinx/CMakeLists.txt

@@ -149,7 +149,7 @@ if(SPHINX_HTML)
           )
 endif()
 if(SPHINX_QTHELP)
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/qthelp/CMake.qch
+  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/qthelp/CMake-${CMake_VERSION_MAJOR}${CMake_VERSION_MINOR}${CMake_VERSION_PATCH}.qch
           DESTINATION ${CMAKE_DOC_DIR}
           )
 endif()