syntax: 'var'->'let' 'function'->'func'

- 'var' has some weird scoping connotations with users of JS. better to change it to 'let', which will decide whether to make the variable a local or a global
- 'func' looks visually appealing lol
- some minor refactoring done in cparse.c

examples/stress.cosmo

@@ -1,15 +1,15 @@
 proto Test
-    function __init(self, x)
+    func __init(self, x)
         self.x = x
     end
 
-    function print(self)
+    func print(self)
         print(self.x)
     end
 end
 
 // stressing the GC
-for (var i = 0; i < 100000; i++) do
-    var x = Test("Hello world " .. i)
+for (let i = 0; i < 100000; i++) do
+    let x = Test("Hello world " .. i)
     x:print()
 end