optimize: fixed misuses of Lua global variables in our Lua code (caught by the new version of the lj-releng tool).

Author: agentzh

lib/ngx/errlog.lua

@@ -18,6 +18,7 @@ local num_value = ffi_new("double[1]")
 local getfenv = getfenv
 local tonumber = tonumber
 local type = type
+local error = error
 
 
 local _M = { version = base.version }

lib/resty/core/base.lua

@@ -52,6 +52,7 @@ end
 local clear_tab
 ok, clear_tab = pcall(require, "table.clear")
 if not ok then
+    local pairs = pairs
     clear_tab = function (tab)
                     for k, _ in pairs(tab) do
                         tab[k] = nil

lib/resty/core/phase.lua

@@ -5,6 +5,7 @@ local C = ffi.C
 local FFI_ERROR = base.FFI_ERROR
 local error = error
 local tostring = tostring
+local getfenv = getfenv
 
 
 ffi.cdef[[