+ FreeImage_OpenMultiBitmapU

* FreeImage_OpenMultiBitmap now thunks to FreeImage_OpenMultiBitmapU
Various bug fixes

! FreeImage_SetTransparentIndex no longer allocates memory
! FreeImage_SetMetadata now fails if it is unable to allocate memory
! FreeImage_OutputMessageProc thunks to vnsprintf (C++11 compiler required!)
! OrderedDispersedDot now fails if it is unable to allocate memory
! LosslessTransform is more rigorous in checking its parameters
! mng_ReadChunks now correctly reads PHYS chunks
! mng_ReadChunks now correctly handles realloc failure
! FreeImage_Initialise now correctly/safely concats paths during plugin detection
! FreeImage_GetFIFFromFilename now fails if it is unable to allocate memory
! FreeImage_GetFIFFromFilenameU now fails if it is unable to allocate memory
! (Bitmap) Save now fails if it is unable to allocate memory
! (GIF) Validate now uses memcmp instead of strncmp to suppress spurious analysis warnings
! rgbe_WriteHeader now checks to see if info is null before writing out the comment blob
! tiff_read_exif_tag now fails if it is unable to allocate memory
! (RAS) Load now fails if it is unable to allocate memory
! (J2K) Save no longer consumes obscene amounts of stack space
! (JP2) Save no longer consumes obscene amounts of stack space
! psdParser::ReadImageData now correctly checks both rle_line/line lengths
! FreeImage_OpenMultiBitmap now fails if it is unable to allocate memory