Build improvements and fix for TTL bug

Makefile:
- remove use of makedepend
- cooperate with CFLAGS from the command line
- improve handling of AVL tar file

bfd.c:
- hide unused variable warnings
- clean up build warnings
- fix bug that would see TTL of 0 on some architectures

bfd.h, tp-timers.h:
- be more dogmatic about include files
put cmsgbuf size back after debugging