String functions are not enabled on 64bit windows

[louist103]

When building on 64 bit Windows with visual studio the build fails because the following functions can not be found:

static bool WReplaceString(std::wstring& str, const std::wstring& oldStr, const std::wstring& newStr);
static std::vector<std::wstring> WSplitStringToVector(const std::wstring& text, char delimiter, bool pushEmpty);
static std::string wstring_to_string(const std::wstring& wstr);
static std::wstring string_to_wstring(const std::string& mbstr);

This is fixed by replacing line 730 in ImGuiFileDialogl.h with:

#if defined(WIN32) || defined(_WIN64)

[aiekick]

thanks. fixed