Better documentation for LUA_ERRERR

Not all errors in a message handler generate a LUA_ERRERR.

ldo.c

@@ -203,7 +203,7 @@ TStatus luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 #define ERRORSTACKSIZE	(MAXSTACK + STACKERRSPACE)
 
 
-/* raise an error while running the message handler */
+/* raise a stack error while running the message handler */
 l_noret luaD_errerr (lua_State *L) {
   TString *msg = luaS_newliteral(L, "error in error handling");
   setsvalue2s(L, L->top.p, msg);
@@ -339,7 +339,7 @@ int luaD_growstack (lua_State *L, int n, int raiseerror) {
        a stack error; cannot grow further than that. */
     lua_assert(stacksize(L) == ERRORSTACKSIZE);
     if (raiseerror)
-      luaD_errerr(L);  /* error inside message handler */
+      luaD_errerr(L);  /* stack error inside message handler */
     return 0;  /* if not 'raiseerror', just signal it */
   }
   else if (n < MAXSTACK) {  /* avoids arithmetic overflows */

manual/manual.of

@@ -270,7 +270,7 @@ print(x)              --> 10  (the global one)
 
 Notice that, in a declaration like @T{local x = x},
 the new @id{x} being declared is not in scope yet,
-and so the @id{x} in the right-hand side refers to the outside variable.
+and so the @id{x} on the right-hand side refers to the outside variable.
 
 Because of the @x{lexical scoping} rules,
 local variables can be freely accessed by functions
@@ -2826,7 +2826,16 @@ status codes to indicate different kinds of errors or other conditions:
 For such errors, Lua does not call the @x{message handler}.
 }
 
-@item{@defid{LUA_ERRERR}| error while running the @x{message handler}.}
+@item{@defid{LUA_ERRERR}|
+stack overflow while running the @x{message handler}
+due to another stack overflow.
+More often than not,
+this error is the result of some other error while running
+a message handler.
+An error in a message handler will call the handler again,
+which will generate the error again, and so on,
+until this loop exhausts the stack and cause this error.
+}
 
 @item{@defid{LUA_ERRSYNTAX}| syntax error during precompilation
 or format error in a binary chunk.}