Add address normalization to isValidECSignature method

[fabioberger]

Description

Fixes: #1095

Testing instructions

Types of changes

Checklist:

• Prefix PR title with [WIP] if necessary.
• Prefix PR title with bracketed package name(s) corresponding to the changed package(s). For example: [sol-cov] Fixed bug.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons.

[coveralls]

Coverage increased (+0.003%) to 85.169% when pulling 6f02a3f on fixIsValidECSignature into 1402119 on development.