Update libraw to 0.17.2

plus gcc6 fix to dcraw_common.cpp

LibRaw 0.17.2
* strncpy usage was not compatible with glibc bounds check
LibRaw 0.17.1
* fixed two errors found by AlphaFuzzer
* phase_one_correct always returns value; handle P1 return codes in
  postprocessing
LibRaw 0.17.0
* Fixed dcraw.c ljpeg_start possibly buffer overrun
* fixed several bugs detected by using American Fuzzy Lop
* C-API extension to support 3DLut Creator
* More metadata parsing/extraction:
  XMP packet extracted (if exists)
  DNG Color information parsed
  GPS data (partially) parsed
  EXIF/Makernotes parsed for used optics (for both RAW files and DNG
  converted by Adobe convertor).
* Exif/Makernotes parser callback (called for each processed tag)
* Sony ARW2.3 decoder:
  params.sony_arw2_hack removed, decoded data are always in 0...17k range
  (note the difference with dcraw!)
  Additional processing options for Sony lossy compression techincal
  analysis.
* Dcraw 9.26 imported (but some changes not approved because Libraw do it
  better) with some exceptions:
  no Pentax K3-II frame selection code
  no built-in JPEG decompressor
* Many improvements in data decoding/processing:
  Correct decoding of black level values from metadata for many formats,
  LibRaw do not rely on hardcoded black levels.
* 224 camera models added to supported camera list. Some of them are new
  (released since LibRaw 0.16 come out), some was supported before, but
  missed from the list.
* Fujifilm F700/S20Pro second frame support

(markd)