* configure.in: Don't use the canonical host name to decide

* configure.in: Don't use the canonical host name to decide
whether `bzero' and `usleep' have declarations --- that's going
back to the bad old days before autoconf.  Remove the call to
AC_CANONICAL_HOST and the subsequent case statement.
(GUILE_FUNC_DECLARED): New m4 macro.  Use it to check for
declarations for `bzero', `usleep', and (new!) `strptime'.
* acconfig.h: (DECLARE_BZERO, DECLARE_USLEEP): Removed.
(MISSING_BZERO_DECL, MISSING_USLEEP_DECL, MISSING_STRPTIME_DECL):
Added.  I think this naming convention is more consistent with the
rest of autoconf; names generally describes the system, not what
the package should do to accomodate the system.
* configure: Regenerated.