Use semicolons instead of commas.

[topecongiro]

Closes #65.

[dtolnay]

This is a bit more complicated because commas are treated as separators with an optional trailing separator, while semicolons need to be treated as terminators.

{ a, b, c } // ok
{ a, b, c, } // ok
{ a; b; c; } // ok
{ a; b; c } // not ok

The pairs of rules that look like this:

$($(#[$Flag_attr:meta])* const $Flag:ident = $value:expr);+
$($(#[$Flag_attr:meta])* const $Flag:ident = $value:expr);+;

need to be replaced by a single rule that looks like this:

$($(#[$Flag_attr:meta])* const $Flag:ident = $value:expr ;)+

[topecongiro]

@dtolnay Thank you for your comment. I will change my PR accordingly.

[alexcrichton]

Looks great to me, thanks @topecongiro! Want to rebase and I'll merge?

[topecongiro]

@alexcrichton Thank you! Rebased.