Added greater than operator for extended_asset

[Avm07]

Change Description

This PR add friend bool extended_asset::operator>( const extended_asset& a, const extended_asset& b )

API Changes

• API Changes

Documentation Additions

• Documentation Additions

[brianjohnson5972]

Approved, but can you also add the operator>= and <= to cover them all?

[brianjohnson5972]

Approved, but can you also add the operator>= and <= to cover them all?

with just return !(a < b) and !(a > b)

[Avm07]

Approved, but can you also add the operator>= and <= to cover them all?

Comparison operators already exist:
https://github.com/Avm07/eosio.cdt/blob/develop/libraries/eosiolib/core/eosio/asset.hpp#L488
https://github.com/Avm07/eosio.cdt/blob/develop/libraries/eosiolib/core/eosio/asset.hpp#L494

[Avm07]

Added missing operators(>,>=,<=) for symbol_code & symbol & extended_symbol