Add hello world, better for loop snippet

UltiSnips/c.snippets

@@ -1,10 +1,16 @@
-snippet hello "Hello World"
-Hallo
+extends cpp
+
+priority 200
+
+snippet helloworld "Hello World"
+#include <stdio.h>
+
+int main(void){(void)printf("Hello World!\n");return 0;}
 endsnippet
 
 snippet for "For-loop head"
-for (${1:int i} = ${2:0}; ${3:i}; ${4:--i}) {
-	$5
+for (${1:int ${2:i}} = ${3:0}; ${4:$2 < $5}; ${6:$2++}) {
+	$7
 }
 $0
 endsnippet