Sync with i386

Sync with i386

\begin{quote}
Compile genassym.c with ordinary ${CFLAGS}.  The (small) needs for
${GEN_CFLAGS} and -U_KERNEL became negative when all all the
genassym.c's were converted to be cross-built.

Makefile.*:
- Cleanups associated with the old genassym.
- Fixed deprecated spelling of ${.IMPSRC} as "$<".
\end{quote}

Submitted by: bde