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

src/clex.h

@@ -57,7 +57,7 @@ typedef enum
     TOKEN_ELSEIF,
     TOKEN_END,
     TOKEN_FOR,
-    TOKEN_FUNCTION,
+    TOKEN_FUNC,
     TOKEN_PROTO,
     TOKEN_IF,
     TOKEN_IN,
@@ -66,7 +66,7 @@ typedef enum
     TOKEN_OR,
     TOKEN_RETURN,
     TOKEN_THEN,
-    TOKEN_VAR,
+    TOKEN_LET,
     TOKEN_WHILE,
 
     TOKEN_ERROR,