connect inline assembly errors from zig back to the source

[andrewrk]

Related to #246 which is for when LLVM emits assembly errors. This issue is for when Zig emits assembly template parsing errors and is a prerequisite of #246. Also related is #215.

comptime {
    asm(
        \\line 1
        \\line 2 %
        \\line 3
    );
}

output:

/home/andy/downloads/zig/build/test.zig:2:5: error: expected a '%' or '['
    asm(
    ^

The error points at the asm keyword which does not help you find where the problem is.