The `serde_struct_impl!` macro has been modified to be compatible
with the serde 1.0 crate, we use this macro and not the `serde_derive`
crate because the latter doesn't support Rust 1.14.0 which is shipped
on Debian stable and we should remain compatible with it.
Two new features were added:
- "serde": enables serialization/deserialization for common types, it pulls
the serde 1.0 dependency.
- "serde-decimal": enables serialization/deserialization for `UDecimal`/`Decimal`,
this pulls the strason 0.4 depdendency and the serde 1.0 dependency.
Signed-off-by: Jean Pierre Dudey <jeandudey@hotmail.com>