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/code.lua

@@ -86,7 +86,7 @@ checkKlist(foo, {1, 1.0, 2, 2.0, 0, 0.0})
 -- testing opcodes
 
 -- check that 'f' opcodes match '...'
-function check (f, ...)
+local function check (f, ...)
   local arg = {...}
   local c = T.listcode(f)
   for i=1, #arg do
@@ -99,7 +99,7 @@ end
 
 
 -- check that 'f' opcodes match '...' and that 'f(p) == r'.
-function checkR (f, p, r, ...)
+local function checkR (f, p, r, ...)
   local r1 = f(p)
   assert(r == r1 and math.type(r) == math.type(r1))
   check(f, ...)
@@ -107,7 +107,7 @@ end
 
 
 -- check that 'a' and 'b' has the same opcodes
-function checkequal (a, b)
+local function checkequal (a, b)
   a = T.listcode(a)
   b = T.listcode(b)
   assert(#a == #b)