Fix ae.c to avoid timers infinite loop.

This fix was suggested by Anthony LaTorre, that provided also a good
test case that was used to verify the fix.

The problem with the old implementation is that, the time returned by
a timer event (that is the time after it want to run again) is added
to the event *start time*. So if the event takes, in order to run, more
than the time it says it want to be scheduled again for running, an
infinite loop is triggered.

src/ae.h

@@ -33,6 +33,8 @@
 #ifndef __AE_H__
 #define __AE_H__
 
+#include <time.h>
+
 #define AE_OK 0
 #define AE_ERR -1
 
@@ -46,6 +48,7 @@
 #define AE_DONT_WAIT 4
 
 #define AE_NOMORE -1
+#define AE_DELETED_EVENT_ID -1
 
 /* Macros */
 #define AE_NOTUSED(V) ((void) V)