sha1 implementation + helper funcs

vlib/builtin/array.v

@@ -225,3 +225,11 @@ fn free(a voidptr) {
 	C.free(a)
 }
 
+pub fn (b []byte) hex() string {
+	mut hex := malloc(b.len*2+1)
+	mut ptr := &hex[0]
+	for i := 0; i < b.len ; i++ {
+		ptr += C.sprintf(ptr, '%02X', b[i])
+	}
+	return string(hex)
+}