Fixed missing dependencies. The critical missing one was of bi-lexer.o
on bi-parser.h. Not having it sometimes (only with `make -j') triggered
a bug suite that led to ordinary cpp output being put in .depend files.
Various bugs (the main one only with `make -j') prevented timely detection
of failure to build and install gnu/usr.bin/cc. Eventually the missing
${WORLDTMP}/usr/libexec/cpp caused ${WORLDTMP}/usr/bin/cpp to be invoked
by cc, and this version of cpp is not suitable for such invocation.
Ordinary cpp output was put in .depend files when cpp terminated options
processing before seeing the -M flag.

Cleaned up.