Get nyancat nyanning in Serenity.

I found a cute program that renders an animated nyancat in the terminal.
This patch adds enough hackery to get it working correctly. :^)

Kernel/Process.cpp

@@ -1425,6 +1425,20 @@ int Process::sys$kill(pid_t pid, int signal)
     return 0;
 }
 
+int Process::sys$usleep(useconds_t usec)
+{
+    if (!usec)
+        return 0;
+
+    sleep(usec / 1000);
+    if (m_wakeup_time > system.uptime) {
+        ASSERT(m_was_interrupted_while_blocked);
+        dword ticks_left_until_original_wakeup_time = m_wakeup_time - system.uptime;
+        return ticks_left_until_original_wakeup_time / TICKS_PER_SECOND;
+    }
+    return 0;
+}
+
 int Process::sys$sleep(unsigned seconds)
 {
     if (!seconds)

Kernel/Process.h

@@ -166,6 +166,7 @@ public:
     int sys$getcwd(char*, size_t);
     int sys$chdir(const char*);
     int sys$sleep(unsigned seconds);
+    int sys$usleep(useconds_t usec);
     int sys$gettimeofday(timeval*);
     int sys$gethostname(char* name, size_t length);
     int sys$get_arguments(int* argc, char*** argv);

Kernel/Syscall.cpp

@@ -62,6 +62,8 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
         break;
     case Syscall::SC_sleep:
         return current->sys$sleep((unsigned)arg1);
+    case Syscall::SC_usleep:
+        return current->sys$usleep((unsigned)arg1);
     case Syscall::SC_gettimeofday:
         return current->sys$gettimeofday((timeval*)arg1);
     case Syscall::SC_get_dir_entries:

Kernel/Syscall.h

@@ -84,6 +84,7 @@
     __ENUMERATE_SYSCALL(gui_set_global_cursor_tracking_enabled) \
     __ENUMERATE_SYSCALL(rmdir) \
     __ENUMERATE_SYSCALL(chmod) \
+    __ENUMERATE_SYSCALL(usleep) \
 
 
 #ifdef SERENITY

Kernel/types.h

@@ -16,6 +16,7 @@ typedef dword uid_t;
 typedef dword gid_t;
 typedef signed_word pid_t;
 typedef dword time_t;
+typedef dword useconds_t;
 typedef dword suseconds_t;
 
 struct timeval {