Avoid excessive name pollution in test files

Test files are more polite regarding the use of globals when locals
would do, and when globals are necessary deleting them after use.

testes/attrib.lua

@@ -85,7 +85,7 @@ local DIR = "libs" .. dirsep
 
 -- prepend DIR to a name and correct directory separators
 local function D (x)
-  x = string.gsub(x, "/", dirsep)
+  local x = string.gsub(x, "/", dirsep)
   return DIR .. x
 end
 
@@ -106,7 +106,7 @@ local function createfiles (files, preextras, posextras)
   end
 end
 
-function removefiles (files)
+local function removefiles (files)
   for n in pairs(files) do
     os.remove(D(n))
   end
@@ -154,10 +154,9 @@ local try = function (p, n, r, ext)
   assert(ext == x)
 end
 
-a = require"names"
+local a = require"names"
 assert(a[1] == "names" and a[2] == D"names.lua")
 
-_G.a = nil
 local st, msg = pcall(require, "err")
 assert(not st and string.find(msg, "arithmetic") and B == 15)
 st, msg = pcall(require, "synerr")
@@ -191,6 +190,7 @@ try("X", "XXxX", AA, "libs/XXxX")
 
 
 removefiles(files)
+NAME, REQUIRED, AA, B = nil
 
 
 -- testing require of sub-packages
@@ -223,7 +223,7 @@ assert(require"P1" == m and m.AA == 10)
 
 
 removefiles(files)
-
+AA = nil
 
 package.path = ""
 assert(not pcall(require, "file_does_not_exist"))
@@ -305,6 +305,7 @@ else
   assert(_ENV.x == "lib1.sub" and _ENV.y == DC"lib1")
   assert(string.find(ext, "libs/lib1", 1, true))
   assert(fs.id(45) == 45)
+  _ENV.x, _ENV.y = nil
 end
 
 _ENV = _G
@@ -338,10 +339,10 @@ print("testing assignments, logical operators, and constructors")
 
 local res, res2 = 27
 
-a, b = 1, 2+3
+local a, b = 1, 2+3
 assert(a==1 and b==5)
 a={}
-function f() return 10, 11, 12 end
+local function f() return 10, 11, 12 end
 a.x, b, a[1] = 1, 2, f()
 assert(a.x==1 and b==2 and a[1]==10)
 a[f()], b, a[f()+3] = f(), a, 'x'
@@ -353,15 +354,15 @@ do
   local a,b,c
   a,b = 0, f(1)
   assert(a == 0 and b == 1)
-  A,b = 0, f(1)
-  assert(A == 0 and b == 1)
+  a,b = 0, f(1)
+  assert(a == 0 and b == 1)
   a,b,c = 0,5,f(4)
   assert(a==0 and b==5 and c==1)
   a,b,c = 0,5,f(0)
   assert(a==0 and b==5 and c==nil)
 end
 
-a, b, c, d = 1 and nil, 1 or nil, (1 and (nil or 1)), 6
+local a, b, c, d = 1 and nil, 1 or nil, (1 and (nil or 1)), 6
 assert(not a and b and c and d==6)
 
 d = 20
@@ -419,6 +420,7 @@ assert(not pcall(function () local a = {[nil] = 10} end))
 assert(a[nil] == undef)
 a = nil
 
+local a, b, c
 a = {10,9,8,7,6,5,4,3,2; [-3]='a', [f]=print, a='a', b='ab'}
 a, a.x, a.y = a, a[-3]
 assert(a[1]==10 and a[-3]==a.a and a[f]==print and a.x=='a' and not a.y)
@@ -455,7 +457,7 @@ while maxint ~= (maxint + 0.0) or (maxint - 1) ~= (maxint - 1.0) do
   maxint = maxint // 2
 end
 
-maxintF = maxint + 0.0   -- float version
+local maxintF = maxint + 0.0   -- float version
 
 assert(maxintF == maxint and math.type(maxintF) == "float" and
        maxintF >= 2.0^14)