<unistd.h> now declares environ(7) if _WANT_ENVIRON.

Note that it is very bad style of programs to access it directly.

libmaxsi/include/unistd.h

@@ -76,6 +76,10 @@ __BEGIN_DECLS
 @include(intn_t.h)
 #endif
 
+#if defined(_WANT_ENVIRON)
+extern char** environ;
+#endif
+
 /* TODO: These are not implemented in libmaxsi/sortix yet. */
 #if defined(__SORTIX_SHOW_UNIMPLEMENTED)
 unsigned alarm(unsigned);