Fixed MicAbsoluteResourceReference path in case of Windows drive letter leading.

[Driolar]

This is to solve issue #980.

[kasperosterbye]

I like the structure og this. It explicitly checks if you are on windows, and if you are it checks if the second character is a $:
That the text fails is due to something else (and is an other issue, which is that OS should by default be as it is now, but then one should in some cases (like in test) say "we are now on windows, or we are now on Linux".

[Driolar]

Running all Microdown tests with Dr. Tests, 17 errors (all in MicTemplatedWriterTest) and 19 failures result.

I am not familiar with pulling practices yet. What is the next step for this PR?

[kasperosterbye]

I am not sure, but now my feeling is that there is no acceptable solution - I believe that their tests and building is done using Linux and Mac, and not Windows.
I have had similar issues where I place the change in overriding the simple method as an extension in some of my own code.
It makes my code work.
But if you think it is annoying, I agree.