some function added.

const char* GetFIFExtensionList(FREE_IMAGE_FORMAT fif);
FIBITMAP* Clone(FIBITMAP* dib);
FIBITMAP* Rescale(FIBITMAP* dib, int dst_width, int dst_height,
FREE_IMAGE_FILTER filter);
FIBITMAP* Rotate(FIBITMAP* dib, double angle, const void* bkcolor =
NULL);
FIBITMAP* RotateEx(FIBITMAP* dib, double angle, double x_shift, double
y_shift, double x_origin, double y_origin, bool use_mask);