Documentation details on DDD
Minor updates to interface document

Discourage use of SolveAllChunks functions.
Say that mode parameter may go away in the future.
Revert "Minor updates to interface document"

This reverts commit 1491323a2db343de03152b96ea1805cde8bdcd06.
Minor changes to interface document

Discourage use of Chunk functions.
Say that mode parameter may go away in the future.
Two typos and one compiler warning in examples

#ifdef was a few lines too low.
threadIndex might as well be used in SolveBoard.cpp
examples Makefiles updated

make depend and also make clean
portab.h fixed for Mac

For some reason nullptr caused problem in some source files, not others, on the Mac with g++.
It seems more general anyway to test for existence than for __clang__.
Updates to test Makefiles

make depend and make clean
Use include/portab.h, delete other one
Update src Makefiles

Mostly make depend and make clean
Merge pull request #12 from sorenhein/cleanup-pre28

Cleanup pre28