* libtiff/tif_dir.c: TIFFSetField(): refuse to set negative values for
TIFFTAG_XRESOLUTION and TIFFTAG_YRESOLUTION that cause asserts when writing
the directory
* libtiff/tif_dirread.c: TIFFReadDirectory(): refuse to read ColorMap or
TransferFunction if BitsPerSample has not yet been read, otherwise reading
it later will cause user code to crash if BitsPerSample > 1
* libtiff/tif_getimage.c: TIFFRGBAImageOK(): return FALSE if LOGLUV with
SamplesPerPixel != 3, or if CIELAB with SamplesPerPixel != 3 or BitsPerSample != 8
* libtiff/tif_next.c: in the "run mode", use tilewidth for tiled images
instead of imagewidth to avoid crash
* tools/bmp2tiff.c: fix crash due to int overflow related to input BMP dimensions
* tools/tiff2pdf.c: fix crash due to invalid tile count (should likely be checked by
libtiff too). Detect invalid settings of BitsPerSample/SamplesPerPixel for CIELAB / ITULAB
* tools/tiffcrop.c: fix crash due to invalid TileWidth/TileHeight
* tools/tiffdump.c: fix crash due to overflow of entry count.
