Clamp synthesized script from evemu format to non-negative delays

Fixes eternal (well, 49 days..) hang due to negative delays when playing back
evemu scripts with timestamps that go backwards.

NEWS

@@ -1,3 +1,8 @@
+0.8.1 (UNRELEASED)
+------------------
+- Fix eternal hang due to negative delays when playing back evemu scripts with
+  timestamps that go backwards.
+
 0.8 (2014-03-20)
 ----------------
 New features:

src/umockdev.vala

@@ -846,6 +846,8 @@ public class Testbed: GLib.Object {
                 first = false;
             } else {
                 delay = (int) (ev_sec - ev.time.tv_sec) * 1000 + (int) (ev_usec - ev.time.tv_usec) / 1000;
+                if (delay < 0)
+                    delay = 0;
             }
             ev.time.tv_sec = ev_sec;
             ev.time.tv_usec = ev_usec;

tests/test-umockdev.c

@@ -1500,7 +1500,8 @@ t_testbed_replay_evemu_events(UMockdevTestbedFixture * fixture, gconstpointer da
   static const char* test_data = "E: 1234.500000 0000 0000 0\n"   /* SYN */
                                  "E: 1234.650000 0002 0000 5  # comment\n"   /* REL X */
                                  "# some comment\n"
-                                 "E: 1234.650000 0002 0001 -11	# comment #2\n" /* REL Y */
+                                 /* slightly go back in time here */
+                                 "E: 1234.649000 0002 0001 -11	# comment #2\n" /* REL Y */
                                  "E: 1235.200000 0001 0174 1\n";  /* KEY_ZOOM */
 
   umockdev_testbed_add_from_string(fixture->testbed,
@@ -1552,7 +1553,7 @@ t_testbed_replay_evemu_events(UMockdevTestbedFixture * fixture, gconstpointer da
   g_assert_cmpint(read(fd, &ev, sizeof(ev)), ==, sizeof(ev));
   g_assert_cmpint(gettimeofday(&tv_end, NULL), ==, 0);
   g_assert_cmpint(ev.time.tv_sec, ==, 1234);
-  g_assert_cmpint(ev.time.tv_usec, ==, 650000);
+  g_assert_cmpint(ev.time.tv_usec, ==, 649000);
   g_assert_cmpint(ev.type, ==, 2);
   g_assert_cmpint(ev.code, ==, 1);
   g_assert_cmpint(ev.value, ==, -11);