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/math.lua

@@ -50,7 +50,7 @@ end
 local msgf2i = "number.* has no integer representation"
 
 -- float equality
-function eq (a,b,limit)
+local function eq (a,b,limit)
   if not limit then
     if floatbits >= 50 then limit = 1E-11
     else limit = 1E-5
@@ -62,7 +62,7 @@ end
 
 
 -- equality with types
-function eqT (a,b)
+local function eqT (a,b)
   return a == b and math.type(a) == math.type(b)
 end
 
@@ -83,7 +83,7 @@ end
 do
   local x = -1
   local mz = 0/x   -- minus zero
-  t = {[0] = 10, 20, 30, 40, 50}
+  local t = {[0] = 10, 20, 30, 40, 50}
   assert(t[mz] == t[0] and t[-0] == t[0])
 end