Bump Cobalt version

- Remove stub for table.pack/table.unpack.
 - Remove Lua 5.3 bitlib stub. We're not on 5.3, there's no
   point emulating it.
 - Change peripheral.call to correctly adjust the error level. This is a
   terrible hack, but I believe the only good option.

It'd be good to remove load as well, but it's a little more complex due
to our injecting of _ENV.

Closes #363

src/main/java/dan200/computercraft/core/apis/FastLuaException.java

@@ -0,0 +1,35 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.apis;
+
+import dan200.computercraft.api.lua.LuaException;
+
+import javax.annotation.Nullable;
+
+/**
+ * A Lua exception which does not contain its stack trace.
+ */
+public class FastLuaException extends LuaException
+{
+    private static final long serialVersionUID = 5957864899303561143L;
+
+    public FastLuaException( @Nullable String message )
+    {
+        super( message );
+    }
+
+    public FastLuaException( @Nullable String message, int level )
+    {
+        super( message, level );
+    }
+
+    @Override
+    public synchronized Throwable fillInStackTrace()
+    {
+        return this;
+    }
+}

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -383,22 +383,30 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                 String methodName = getString( args, 1 );
                 Object[] methodArgs = Arrays.copyOfRange( args, 2, args.length );
 
-                if( side != null )
+                if( side == null ) throw new LuaException( "No peripheral attached" );
+
+                PeripheralWrapper p;
+                synchronized( m_peripherals )
                 {
-                    PeripheralWrapper p;
-                    synchronized( m_peripherals )
-                    {
-                        p = m_peripherals[side.ordinal()];
-                    }
-                    if( p != null )
-                    {
-                        return p.call( context, methodName, methodArgs );
-                    }
+                    p = m_peripherals[side.ordinal()];
+                }
+                if( p == null ) throw new LuaException( "No peripheral attached" );
+
+                try
+                {
+                    return p.call( context, methodName, methodArgs );
+                }
+                catch( LuaException e )
+                {
+                    // We increase the error level by one in order to shift the error level to where peripheral.call was
+                    // invoked. It would be possible to do it in Lua code, but would add significantly more overhead.
+                    if( e.getLevel() > 0 ) throw new FastLuaException( e.getMessage(), e.getLevel() + 1 );
+                    throw e;
                 }
-                throw new LuaException( "No peripheral attached" );
             }
             default:
                 return null;
         }
     }
+
 }

src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -92,6 +92,7 @@ public class CobaltLuaMachine implements ILuaMachine
         m_globals.load( state, new MathLib() );
         m_globals.load( state, new CoroutineLib() );
         m_globals.load( state, new Bit32Lib() );
+        m_globals.load( state, new Utf8Lib() );
         if( ComputerCraft.debug_enable ) m_globals.load( state, new DebugLib() );
 
         // Remove globals we don't want to expose