Stopped timers don't trigger on TIMER ON

If a timer expires while stopped, it should trigger when TIMER ON is
run. Instead, on QB64 it triggers randomly after the TIMER ON happens.

The basic issue is that `qbevent` needs to be set to trigger the timer,
but TIMER ON doesn't do that. The regular timer logic that does that
already set it when the timer expired while sleeping, so it won't set it
again. The simplest solution is to just alway set qbevent = 1 when TIMER
ON is done. It's slightly less efficent but doesn't hurt to set it even
when there are no timers that expired.

Fixes: #293

internal/c/qbx.cpp

@@ -2073,6 +2073,9 @@ void sub_timer(int32 i, int32 option, int32 passed) {
     // ref: uint8 active;//0=OFF, 1=ON, 2=STOP
     if (option == 1) { // ON
         ontimer[i].active = 1;
+
+        // This is necessary so that if a timer triggered while stopped we will run it now.
+        qbevent = 1;
         return;
     }
     if (option == 2) { // OFF

tests/compile_tests/timer/timer_delayed_run.bas

@@ -0,0 +1,15 @@
+$Console:Only
+
+On Timer(2) GoSub timerhand
+
+' This first delay should not matter
+_Delay 3
+Timer On
+
+' The timer should be triggered twice
+_Delay 5
+System
+
+timerhand:
+Print "Timer!"
+return

tests/compile_tests/timer/timer_delayed_run.output

@@ -0,0 +1,2 @@
+Timer!
+Timer!

tests/compile_tests/timer/timer_first_run.bas

@@ -0,0 +1,12 @@
+$Console:Only
+
+On Timer(2) GoSub timerhand
+Timer On
+
+' Timer should be triggered twice
+_Delay 5
+System
+
+timerhand:
+Print "Timer!"
+return

tests/compile_tests/timer/timer_first_run.output

@@ -0,0 +1,2 @@
+Timer!
+Timer!

tests/compile_tests/timer/timer_stop.bas

@@ -0,0 +1,18 @@
+$Console:Only
+
+On Timer(2) GoSub timerhand
+Timer On
+Timer Stop
+
+' Timer will not trigger when stopped
+Sleep 3
+
+' Timer should trigger immediately when started as two seconds have elapsed
+' while it was stopped
+Timer On
+Timer Off 'Shouldn't matter, timer triggers as soon as Timer On runs
+System
+
+timerhand:
+Print "Timer!"
+return

tests/compile_tests/timer/timer_stop.output

@@ -0,0 +1 @@
+Timer!