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/verybig.lua

@@ -52,7 +52,7 @@ if _soft then return 10 end
 print "testing large programs (>64k)"
 
 -- template to create a very big test file
-prog = [[$
+local prog = [[$
 
 local a,b
 
@@ -85,7 +85,7 @@ function b:xxx (a,b) return a+b end
 assert(b:xxx(10, 12) == 22)   -- pushself with non-constant index
 b["xxx"] = undef
 
-s = 0; n=0
+local s = 0; local n=0
 for a,b in pairs(b) do s=s+b; n=n+1 end
 -- with 32-bit floats, exact value of 's' depends on summation order
 assert(81800000.0 < s and s < 81860000 and n == 70001)
@@ -93,7 +93,7 @@ assert(81800000.0 < s and s < 81860000 and n == 70001)
 a = nil; b = nil
 print'+'
 
-function f(x) b=x end
+local function f(x) b=x end
 
 a = f{$3$} or 10
 
@@ -118,7 +118,7 @@ local function sig (x)
   return (x % 2 == 0) and '' or '-'
 end
 
-F = {
+local F = {
 function ()   -- $1$
   for i=10,50009 do
     io.write('a', i, ' = ', sig(i), 5+((i-10)/2), ',\n')
@@ -138,14 +138,14 @@ function ()   -- $3$
 end,
 }
 
-file = os.tmpname()
+local file = os.tmpname()
 io.output(file)
 for s in string.gmatch(prog, "$([^$]+)") do
   local n = tonumber(s)
   if not n then io.write(s) else F[n]() end
 end
 io.close()
-result = dofile(file)
+local result = dofile(file)
 assert(os.remove(file))
 print'OK'
 return result