[CMake] Patch for Sphinx warning message

[Brad King]

On 07/14/2015 01:13 PM, Brad King wrote:
> Applied with slight tweaks:
>  Utilities/Sphinx: Use 'classic' theme for Sphinx >= 1.3
>  http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=e59a7d7e
[snip]
On 07/14/2015 06:56 PM, Andrew Maclean wrote:
> Thanks, that looks much better than what I did!

I had to revert it because other places in the sphinx config
reference 'default':

 $ git grep -E 'default\>' -- Utilities/Sphinx/
 Utilities/Sphinx/apply_qthelp_css_workaround.cmake:file(READ "${CSS_DIR}/default.css" DefaultCssContent)
 Utilities/Sphinx/apply_qthelp_css_workaround.cmake:  "@import url(\"default.css\")" "${DefaultCssContent}"
 Utilities/Sphinx/conf.py.in:html_theme = 'default'
 Utilities/Sphinx/static/cmake.css:@import url("default.css");

The change above only worked in local testing because some files
were left around in the build tree from the old configuration.

Switching the theme name to 'classic' while still being compatible
with Sphinx <= 1.2 would require a dedicated effort to make the
entire static/ directory and other supporting scripts all configured
based on the Sphinx version.

It looks like even sphinx upstream has dropped the warning:

 theming: do not warn if theme is "default"
 https://github.com/sphinx-doc/sphinx/commit/034c4e942451fad40350ae3bb3beda6c63a49064

-Brad