add fgetpwent (nonstandard function)

based on patch by Jeremy Huntwork
diff --git a/include/pwd.h b/include/pwd.h
index 38e856d..fbdda3e 100644
--- a/include/pwd.h
+++ b/include/pwd.h
@@ -9,6 +9,10 @@
 #define __NEED_uid_t
 #define __NEED_gid_t
 
+#ifdef _GNU_SOURCE
+#define __NEED_FILE
+#endif
+
 #include <bits/alltypes.h>
 
 struct passwd
@@ -33,6 +37,7 @@
 
 #ifdef _GNU_SOURCE
 char *getpass(const char *);
+struct passwd *fgetpwent(FILE *);
 #endif
 
 #ifdef __cplusplus