Add support for static if blocks within inline asm

This is a fairly simply change to the parser to allow `static if` blocks within inline asm statements. Allowing these within inline asm statements allows for significantly cleaner templated inline asm. Feel free to discuss whether this is actually a good thing or not. I would add a test-case to the unittests, but I haven't gotten around to making the DMD tests run on my machine yet, I will likely add a test to the suite either tonight or tomorrow.