Improved lume.clamp()'s performance on non-JIT

Removed use of the functions math.max() and math.min() and replaced them
with and/ors:

[5000000 calls, Lua5.2]
old func: 1.37 seconds
new func: 0.53 seconds

lume.lua

@@ -11,7 +11,7 @@ local lume = { _version = "1.1.0" }
 
 
 function lume.clamp(x, min, max)
-  return math.max(math.min(x, max), min)
+  return x < min and min or (x > max and max or x)
 end