Local portab_DDD.h file

Also call SetMaxThreads(0) (even for Windows, doesn't hurt).
<sys/time.h> is in portab_DDD.h, so not needed in timer.cpp (and would have
needed to be included only on certain systems).
Updated Makefiles

Mostly make depend and make clean
Merge pull request #1 from sorenhein/cleanup-pre28

Cleanup pre28