Fix echo, shorten file size

src/echo.c

@@ -1,10 +1,9 @@
-#include <string.h>
 #include <stdio.h>
-#include <unistd.h>
 
 int
 main(int argc, char *argv[])
 {
+  ++argv;
   while(*argv) {
     (void)fputs(*argv, stdout);   // Print argv
     if(*++argv) putchar(' ');     // If multiple things in argv, print a space between them.