c: init array with string literals not introduced. (#2369)

* c: fix using pointer before introduced.

* c: init array with string literals not introduced.

To avoid using the concept pointer before it has been introduced,
previously it is changed to array.
But as @geoffliu pointed out,
array initialization using string literals is not introduced either.
So this commit uses neither pointer nor array.
Discussing `i++` and `++i` does not need to involve pointer or array.

* c: use `var = value` instead of `->`.

`->` is typically used for functions.
Thanks, @vendethiel.

c.html.markdown

@@ -236,11 +236,9 @@ int main (int argc, char** argv)
   z = (e > f) ? e : f; // => 10 "if e > f return e, else return f."
 
   // Increment and decrement operators:
-  char *s = "ILoveC";
   int j = 0;
-  s[j++]; // => "I". Returns the j-th item of s THEN increments value of j.
-  j = 0;
-  s[++j]; // => "L". Increments value of j THEN returns j-th value of s.
+  int s = j++; // Return j THEN increase j. (s = 0, j = 1)
+  s = ++j; // Increase j THEN return j. (s = 2, j = 2)
   // same with j-- and --j
 
   // Bitwise operators!