If a Markdown document contains an embedded machine that specifies a version number (eg, "1.15.6"), then the web server will switch to serving a compiled version, since that's the only way it can guarantee the requested version
I spent some time fixing the latter because browsers have started warning that synchronous XMLHttpRequest calls on the "main thread" (as Firefox calls it) are deprecated. Since the days of such calls seems to be numbered, I decided to act sooner rather than later. All PCjs XMLHttpRequests go through a single library function (weblib.loadResource), which accepts an fAsync parameter, and the only code that is still allowed to pass false for that parameter are "emergency" shutdown requests (which I believe browsers must still allow).
