THRIFT-2506 Update TProtocolException error codes to be used consistently throughout the library

Patch: Jens Geyer
diff --git a/lib/lua/TProtocol.lua b/lib/lua/TProtocol.lua
index 9eb94f5..616e167 100644
--- a/lib/lua/TProtocol.lua
+++ b/lib/lua/TProtocol.lua
@@ -26,7 +26,7 @@
   SIZE_LIMIT       = 3,
   BAD_VERSION      = 4,
   INVALID_PROTOCOL = 5,
-  MISSING_REQUIRED_FIELD = 6,
+  DEPTH_LIMIT      = 6,
   errorCode        = 0,
   __type = 'TProtocolException'
 }
@@ -41,8 +41,8 @@
     return 'Bad version'
   elseif self.errorCode == self.INVALID_PROTOCOL then
     return 'Invalid protocol'
-  elseif self.errorCode == self.MISSING_REQUIRED_FIELD then
-    return 'Missing required field'
+  elseif self.errorCode == self.DEPTH_LIMIT then
+    return 'Exceeded size limit'
   else
     return 'Default (unknown)'
   end