[Doxygen-develop] Support for MathJax extensions (patch)

[David M. <mu...@gm...>]

Hello,

This is my first patch, so I am not sure if this is the proper way to submit
it.
This adds support for MathJax extensions through the MATHJAX_EXTENSIONS
config option. For example, use:
MATHJAX_EXTENSIONS     = TeX/AMSmath TeX/AMSsymbols

Best regards,

David Munger