Support basic inout params for C->Lua
Fix typo in format() call

The second format variable was being passed to error().
Warn when a nothrow callback raises an error
Merge pull request #85 from gregier/inout-from-c

Support basic inout params for C->Lua
Merge pull request #87 from gregier/typo

Fix typo in format() call
Merge pull request #86 from gregier/warn-nothrow-error

Warn when a nothrow callback raises an error
Small cosmetic changes for callable_tostring