Add support for libevent-style timed events. Adding a timed event

is currently O(n).  The only consumer of timed events is sudoreplay
which only used a singled one so O(n) == O(1) for now.  This also
allows us to remove the nanosleep compat function as we now use a
timeout event instead.

include/missing.h

@@ -186,13 +186,6 @@
 #undef ISSET
 #define ISSET(t, f)     ((t) & (f))
 
-/*
- * Some systems define this in <sys/param.h> but we don't include that anymore.
- */
-#ifndef howmany
-# define howmany(x, y)	(((x) + ((y) - 1)) / (y))
-#endif
-
 /*
  * Older systems may be missing stddef.h and/or offsetof macro
  */
@@ -413,9 +406,6 @@ char *mkdtemp(char *);
 #ifndef HAVE_MKSTEMPS
 int mkstemps(char *, int);
 #endif
-#ifndef HAVE_NANOSLEEP
-int nanosleep(const struct timespec *, struct timespec *);
-#endif
 #ifndef HAVE_PW_DUP
 struct passwd *pw_dup(const struct passwd *);
 #endif