Virtual consoles kinda work!

We now make three VirtualConsoles at boot: tty0, tty1, and tty2.
We launch an instance of /bin/sh in each one.
You switch between them with Alt+1/2/3

How very very cool :^)

Kernel/TTY.cpp

@@ -11,15 +11,30 @@ TTY::~TTY()
 
 ssize_t TTY::read(byte* buffer, size_t size)
 {
-    return 0;
+    ssize_t nread = min(m_buffer.size(), size);
+    memcpy(buffer, m_buffer.data(), nread);
+    if (nread == m_buffer.size())
+        m_buffer.clear();
+    else {
+        dbgprintf("had %u, read %u\n", m_buffer.size(), nread);
+        ASSERT_NOT_REACHED();
+    }
+    return nread;
 }
 
 ssize_t TTY::write(const byte* buffer, size_t size)
 {
+    for (size_t i = 0; i < size; ++i)
+        onTTYWrite(buffer[i]);
     return 0;
 }
 
 bool TTY::hasDataAvailableForRead() const
 {
-    return false;
+    return !m_buffer.isEmpty();
+}
+
+void TTY::emit(byte ch)
+{
+    m_buffer.append(ch);
 }