#276 Fix memory access violation when parsing datetime types (#360)
#276 Fix memory access violation when parsing datetime types (#360)

* #276 Fix memory access violation when parsing datetime types

- Replace char* with std::string to persist the memory content and avoid memory access violation when restoring old locale
- Second call to setlocale frees the old_lc_time pointer which causes the memory access violation during restore (3rd call)

* Fix possibility of dereferencing nullptr when assigning C String to std::string

- C strings can be null
nanodbc/nanodbc,nanodbc/nanodbc