ports-gcc: add missing headers

Index: src/sp.cpp
--- src/sp.cpp.orig
+++ src/sp.cpp
@@ -8,9 +8,11 @@
 using namespace scim;
 
 #include <stdio.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <limits.h>
 #include <ctype.h>
+#include <unistd.h>
 
 #include "main.h"
 #include "sp.h"