Add input_grayscale_image_pyramid

libjpeg not being able to open some types of jpeg file.

* Upgrades dlib's included libjpeg to version 8d

* Overloads load_jpeg to read from memory buffer

* Removes "__inline__" define in jconfig, broke VC build

* Changes buffer size type to size_t

These warnings occurred when building the semantic segmentation
examples

* prevent GCC from complaining about this unused parameter

* fix some pedantic warnings

* remove unneeded assert

given an empty list of initial function evaluations.

* Semantic-segmentation loss calculation: fix buffer usage on multi-GPU training

* Review fix: make the work buffer live longer