Try to get HTML Help to render SVG.

Add a custom stylesheet that inserts

    <meta http-equiv="X-UA-Compatible" content="IE=9" >

at the top of our HTML Help output. This *should* convince the
WebBrowser control to draw our new SVG images.

Change-Id: Iae491128195d3738951f3d19e2f82dd3fc73d1d8
Reviewed-on: https://code.wireshark.org/review/3814
Reviewed-by: Gerald Combs <gerald@wireshark.org>