Various warning fixes and devirtualization

* Remove ArrayString
* devirtualize GetCount and SetCount, they're no longer needed
* set storage duration of fmt::placeholder to extern to be consistent
* make length unsigned and the return value of sprintf signed
* remove dead code "s.Close()" is never reached
* devirtualize WrteToLog()
* devirtualize Ini functions
Merge pull request #177 from Bigpet/minifix

Various warning fixes and devirtualization