Multiline comments with `//` in them before closing `*)` are broken in GitHub colorization

[Lincoln Atkinson]

I noticed that the bottom ~75% of https://github.com/Microsoft/visualfsharp/blob/fsharp4/src/fsharp/build.fs#L973 is incorrectly greyed out.

Looking at the point where it starts, my hunch is that if a // sequence is inside a multi-line comment (* ... *) it somehow causes the close of the multiline comment to be ignored.

[Robert Jeppesen]

let a = 123
(* narrowing it down
  multiline comment // is fine
*)
let b = 23
(* things seem to break when // is on the same line as comment close -> *)
let c = 3

[Robert Jeppesen]

@latkin Hey, cool, its been picked up by Github already! https://github.com/Microsoft/visualfsharp/blob/fsharp4/src/fsharp/build.fs#L973

[Lincoln Atkinson]

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