add interface for timedwait on semaphores

According to SDL documentation, the SDL implementation of timedwait may
suck on some platforms, so it should only be used, where high CPU usage
during the wait is no issue.

getpckserver() will now only wait for one second for access to the
package server list and return an error instead of waiting indefinitely.

source/src/tools.cpp

@@ -543,6 +543,11 @@ int sl_semaphore::trywait()
     return SDL_SemTryWait((SDL_sem *) data);
 }
 
+int sl_semaphore::timedwait(int howlongmillis)
+{
+    return SDL_SemWaitTimeout((SDL_sem *) data, howlongmillis);
+}
+
 int sl_semaphore::getvalue()
 {
     return SDL_SemValue((SDL_sem *) data);
@@ -579,6 +584,20 @@ int sl_semaphore::trywait()
     return sem_trywait((sem_t *) data);
 }
 
+int sl_semaphore::timedwait(int howlongmillis)
+{
+    struct timespec t;
+    if(clock_gettime(CLOCK_REALTIME, &t))
+    {
+        (*errorcount)++;
+        return sem_trywait((sem_t *) data);
+    }
+    howlongmillis += t.tv_nsec / 1000000;
+    t.tv_nsec = (howlongmillis % 1000) * 1000000;
+    t.tv_sec += howlongmillis / 1000;
+    return sem_timedwait((sem_t *) data, &t);
+}
+
 int sl_semaphore::getvalue()
 {
     int ret;