bmp_img_read need some verification for "Bits Per Pixel" and "Compression"

[DeqingSun]

The current bmp_img_read function only supports 24 bit uncompressed BMP.

Some code like

if ((img->img_header.biBitCount != 24) || (img->img_header.biCompression != 0)){
		printf("format is not 24bit uncompressed\n");
		fclose (img_file);
		return BMP_ERROR;
	}

will be helpful to avoid errors and give user an idea about the error.