Add settings and isa command-line options to cton-util wasm. (#158)

* Add settings and isa command-line options to cton-util wasm.

* Use map_err to simplify error handling.

* Use `&*` instead of `.borrow()`.

lib/reader/src/lib.rs

@@ -11,7 +11,7 @@ pub use error::{Location, Result, Error};
 pub use parser::{parse_functions, parse_test};
 pub use testcommand::{TestCommand, TestOption};
 pub use testfile::{TestFile, Details, Comment};
-pub use isaspec::IsaSpec;
+pub use isaspec::{IsaSpec, parse_options};
 pub use sourcemap::SourceMap;
 
 mod error;