* Prevent reentrancy by disallowing default context values

* Combine with gas checks

Also use a default context value for ovmNumber and blockNumber

* remove unused code

* fix re-entrancy reversions

* clean up comment

* actually fix test value

* swap validity condition for nonreentrant input

* fix gas spec

* address PR feedback

* linting
Co-authored-by: Ben Jones <ben@pseudonym.party>