add b64_ntop checking and fallback for nc(1)

include/Makefile.am

@@ -11,6 +11,7 @@ noinst_HEADERS += compat/err.h
 noinst_HEADERS += compat/netdb.h
 noinst_HEADERS += compat/poll.h
 noinst_HEADERS += compat/readpassphrase.h
+noinst_HEADERS += compat/resolv.h
 noinst_HEADERS += compat/stdio.h
 noinst_HEADERS += compat/stdlib.h
 noinst_HEADERS += compat/string.h

include/compat/readpassphrase.h

@@ -37,11 +37,7 @@
 #define RPP_SEVENBIT    0x10		/* Strip the high bit from input. */
 #define RPP_STDIN       0x20		/* Read from stdin, not /dev/tty */
 
-#include <sys/cdefs.h>
-
-__BEGIN_DECLS
 char * readpassphrase(const char *, char *, size_t, int);
-__END_DECLS
 
 #endif /* !_READPASSPHRASE_H_ */
 

include/compat/resolv.h

@@ -0,0 +1,24 @@
+/*
+ * Public domain
+ * resolv.h compatibility shim
+ */
+
+#ifndef LIBCRYPTOCOMPAT_RESOLV_H
+#define LIBCRYPTOCOMPAT_RESOLV_H
+
+#ifdef _MSC_VER
+#if _MSC_VER >= 1900
+#include <../ucrt/resolv.h>
+#else
+#include <../include/resolv.h>
+#endif
+#else
+#include_next <resolv.h>
+#endif
+
+#ifndef HAVE_B64_NTOP
+int b64_ntop(unsigned char const *, size_t, char *, size_t);
+int b64_pton(char const *, unsigned char *, size_t);
+#endif
+
+#endif