More minor bugfixes

- make pollcat_loop() work as expected with no structs linked, by
  - calling usleep() instead of poll()
  - refactoring delay calculation and reset into pollcat_time_value()
- simplify pollcat_timer_dispatch() in case of slow callbacks
  - deprecate pollcat_timer_dispatch_thresh
- revise tests/timer.c to support two new options:
  - -s to monitor stdin with pollcat_fd_add()
  - -w to use pollcat_loop() instead of handling main-loop separately
- make pollcat_dump() always present in header, since it's always compiled in
- add Makefile rules for installing tests, for easier running on cross-compiled targets

src/pollcat.c

@@ -1,7 +1,7 @@
 /** Wrapper structure for poll()
  *
  *  This file is part of the Pollcat Library.
- *  Copyright (C) 2022 Expatria Technologies Inc.
+ *  Copyright (C) 2022,2025 Expatria Technologies Inc.
  *  Contact: Morgan Hughes <morgan@expatria.ca>
  *
  *  The Pollcat Library is free software: you can redistribute it and/or modify it under
@@ -284,6 +284,23 @@ void pollcat_time_reduce (int time)
 		pollcat_time_current = time;
 }
 
+/** Return the current timeout and reset the current timeout to the base value
+ *
+ *  \return  Timeout in milliseconds
+ */
+int pollcat_time_value (void)
+{
+	/* latch current value, which may have been reduced by pollcat_time_reduce() */
+	int value = pollcat_time_current;
+
+	/* enforce minimum */
+	if ( value < pollcat_time_minimum )
+		value = pollcat_time_minimum;
+
+	/* reset to base before return, for next call */
+	pollcat_time_current = pollcat_time_base;
+	return value;
+}
 
 /** Wraps the system poll() command using the internal pollfd array and timeout
  *
@@ -296,11 +313,7 @@ int pollcat_poll (void)
 	/* Auto init, no-return if failed */
 	pollcat_init();
 
-	if ( pollcat_time_current < pollcat_time_minimum )
-		pollcat_time_current = pollcat_time_minimum;
-
-	ret = poll(pollcat_list, pollcat_used, pollcat_time_current);
-	pollcat_time_current = pollcat_time_base;
+	ret = poll(pollcat_list, pollcat_used, pollcat_time_value());
 
 	return ret;
 }