Fix norton/lets#8 - impl_destroy/6 is calling a wrong port function.
Fix norton/lets#9 - a typo in lets_output_delete2().
Fix a typo in README.md; "make eqc" should read "make compile-for-eqc".
Merge pull request #11 from tatsuya6502/impl_drv_typo_fix

Impl_drv typo fixes - norton/lets#8 and norton/lets#9