Fix for Microsoft Edge/Windows 10
The Microsoft Edge browser dropped support for ActiveX, which meant that all IE-related hacks were no longer triggered. Which would have been fine if Edge had actually eliminated the need for any IE-related hacks. Unfortunately, there was still one hack that Edge needed: stripping the <DOCTYPE> from XSL files before loading them into the browser's XSLTProcessor.
In an effort to streamline PCjs browser support, I now strip the <DOCTYPE> from XSL files in all cases. Current versions of Chrome, Safari and Firefox seem to be OK with that change, so hopefully this is the last time I have to deal with browser-specific nonsense -- at least in the realm of XML and XSLT processing.
The PCjs loader in embed.js still contains the old ActiveX work-arounds, so PCjs should continue to run fine in IE v9 through v11.