swap*.c files if they haven't changed from the last time config was
run, so that less stuff will need to be rebuilt (ie, assym.h, upon
which many other things depend) each time config is rerun.
round has been tested on Solaris/x86 and Linux hosts.
* Add host tools cap_mkdb, ctags, m4, uudecode.
* Protect __RCSID() and __COPYRIGHT() better.
* Reduce the number of places that need to include "config.h", to keep
sources closer to their "vanilla" versions.
* Add more compat #defines and autoconf-checked functions.
