add compat getopt implementation, remove patches

This adds a getopt implementation for compatibility where it is not
available, removing a couple of regress patches.

Note, this is a slightly modified copy from OpenBSD libc that doesn't
expose getopt_long, which has dependency conflicts with Windows system
headers and isn't needed anyway.

include/compat/unistd.h

@@ -64,6 +64,10 @@ int getentropy(void *buf, size_t buflen);
 #endif
 #endif
 
+#ifndef HAVE_GETOPT
+#include <getopt.h>
+#endif
+
 #ifndef HAVE_GETPAGESIZE
 int getpagesize(void);
 #endif