Gmoshkin/helper macros

Summary

• feat: static_assert!, size_of! & offset_of! macros

• feat: doc-comments for c_str! & c_ptr! macros + compile time checking

• doc: doc-comments for tarantool::ser_and_get_error! macro

Ensure that

• New code is covered by tests
• API is documented
• Changelog is up to date
• Version is bumped in the appropriate Cargo.toml files