We would like the codebase to be optimized for readability not ease of
development, as such code that is write-once-read-many should not use
macros.
Currently we use the `impl_std_error` macro to implement
`std::error::Error` for struct error types. This makes the code harder
to read at a glance because one has to think what the macro does.
Remove the `impl_std_error` macro and write the code explicitly.
This implements basic facilities to conditionally carry string inputs in
parse errors. This includes:
* `InputString` type that may carry the input and format it
* `parse_error_type!` macro creating a special type for parse errors
* `impl_parse` implementing parsing for various types as well as its
`serde`-supporting alternative
Tobin C. Harding
Martin Habovstiak