Merge pull request #298 from SquidDev-CC/ComputerCraft/feature/luaj-bit32

Replace BitAPI with a LuaJ implementation of bit32

src/main/resources/assets/computercraft/lua/bios.lua

@@ -55,18 +55,6 @@ if _VERSION == "Lua 5.1" then
     table.unpack = unpack
     table.pack = function( ... ) return { n = select( "#", ... ), ... } end
 
-    -- Install the bit32 api
-    local nativebit = bit
-    bit32 = {}
-    bit32.arshift = nativebit.brshift
-    bit32.band = nativebit.band
-    bit32.bnot = nativebit.bnot
-    bit32.bor = nativebit.bor
-    bit32.btest = function( a, b ) return nativebit.band(a,b) ~= 0 end
-    bit32.bxor = nativebit.bxor
-    bit32.lshift = nativebit.blshift
-    bit32.rshift = nativebit.blogic_rshift
-
     if _CC_DISABLE_LUA51_FEATURES then
         -- Remove the Lua 5.1 features that will be removed when we update to Lua 5.2, for compatibility testing.
         -- See "disable_lua51_functions" in ComputerCraft.cfg
@@ -76,11 +64,21 @@ if _VERSION == "Lua 5.1" then
         unpack = nil
         math.log10 = nil
         table.maxn = nil
-        bit = nil
+    else
+        -- Inject a stub for the old bit library
+        _G.bit = {
+            bnot = bit32.bnot,
+            band = bit32.band,
+            bor = bit32.bor,
+            bxor = bit32.bxor,
+            brshift = bit32.arshift,
+            blshift = bit32.lshift,
+            blogic_rshift = bit32.rshift
+        }
     end
 end
 
-if _VERSION == "Lua 5.3" then
+if _VERSION == "Lua 5.3" and not bit32 then
     -- If we're on Lua 5.3, install the bit32 api from Lua 5.2
     -- (Loaded from a string so this file will still parse on <5.3 lua)
     load( [[