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/db.lua

@@ -16,7 +16,7 @@ end
 assert(not debug.gethook())
 
 local testline = 19         -- line where 'test' is defined
-function test (s, l, p)     -- this must be line 19
+local function test (s, l, p)     -- this must be line 19
   collectgarbage()   -- avoid gc during trace
   local function f (event, line)
     assert(event == 'line')
@@ -50,7 +50,7 @@ end
 
 
 -- test file and string names truncation
-a = "function f () end"
+local a = "function f () end"
 local function dostring (s, x) return load(s, x)() end
 dostring(a)
 assert(debug.getinfo(f).short_src == string.format('[string "%s"]', a))
@@ -72,7 +72,8 @@ dostring(a, string.format("=%s", string.rep('x', 500)))
 assert(string.find(debug.getinfo(f).short_src, "^x*$"))
 dostring(a, "=")
 assert(debug.getinfo(f).short_src == "")
-a = nil; f = nil;
+_G.a = nil; _G.f = nil;
+_G[string.rep("p", 400)] = nil
 
 
 repeat
@@ -120,6 +121,7 @@ else
 end
 ]], {2,3,4,7})
 
+
 test([[
 local function foo()
 end
@@ -128,6 +130,7 @@ A = 1
 A = 2
 A = 3
 ]], {2, 3, 2, 4, 5, 6})
+_G.A = nil
 
 
 test([[--
@@ -175,6 +178,8 @@ end
 
 test([[for i=1,4 do a=1 end]], {1,1,1,1})
 
+_G.a = nil
+
 
 do   -- testing line info/trace with large gaps in source
 
@@ -194,6 +199,7 @@ do   -- testing line info/trace with large gaps in source
     end
   end
 end
+_G.a = nil
 
 
 do   -- testing active lines
@@ -287,7 +293,6 @@ foo(200, 3, 4)
 local a = {}
 for i = 1, (_soft and 100 or 1000) do a[i] = i end
 foo(table.unpack(a))
-a = nil
 
 
 
@@ -307,13 +312,14 @@ do   -- test hook presence in debug info
   debug.sethook()
   assert(count == 4)
 end
+_ENV.a = nil
 
 
 -- hook table has weak keys
 assert(getmetatable(debug.getregistry()._HOOKKEY).__mode == 'k')
 
 
-a = {}; L = nil
+a = {}; local L = nil
 local glob = 1
 local oldglob = glob
 debug.sethook(function (e,l)
@@ -354,7 +360,7 @@ function foo()
 end; foo()  -- set L
 -- check line counting inside strings and empty lines
 
-_ = 'alo\
+local _ = 'alo\
 alo' .. [[
 
 ]]
@@ -403,6 +409,7 @@ function g(a,b) return (a+1) + f() end
 
 assert(g(0,0) == 30)
  
+_G.f, _G.g = nil
 
 debug.sethook(nil);
 assert(not debug.gethook())
@@ -446,7 +453,7 @@ local function collectlocals (level)
 end
 
 
-X = nil
+local X = nil
 a = {}
 function a:f (a, b, ...) local arg = {...}; local c = 13 end
 debug.sethook(function (e)
@@ -469,6 +476,7 @@ a:f(1,2,3,4,5)
 assert(X.self == a and X.a == 1   and X.b == 2 and X.c == nil)
 assert(XX == 12)
 assert(not debug.gethook())
+_G.XX = nil
 
 
 -- testing access to local variables in return hook (bug in 5.2)
@@ -593,6 +601,7 @@ end
 
 debug.sethook()
 
+local g, g1
 
 -- tests for tail calls
 local function f (x)
@@ -638,7 +647,7 @@ h(false)
 debug.sethook()
 assert(b == 2)   -- two tail calls
 
-lim = _soft and 3000 or 30000
+local lim = _soft and 3000 or 30000
 local function foo (x)
   if x==0 then
     assert(debug.getinfo(2).what == "main")
@@ -940,7 +949,7 @@ end
 
 
 print("testing debug functions on chunk without debug info")
-prog = [[-- program to be loaded without debug information (strip)
+local prog = [[-- program to be loaded without debug information (strip)
 local debug = require'debug'
 local a = 12  -- a local variable