Use separate patch for try syntax

I tend to run "git push-to-try ..." and then simultaneously post to Bugzilla using the patches in the hg repo's git-temp queue.

However, this approach currently breaks down a bit, because git push-to-try mangles the commit message of the last patch to throw in the try syntax at the front, which then displeased the sheriffs when I unknowingly left this format in my uploaded patch. 

This changes moves the try syntax to it's own empty patch, leaving the commit messages of actual code patches alone.