Keep openSSH-portable's blowfish code unmodified

and use a stub "includes.h".

This also fixes build issues against musl-libc, which does not
implicitly include <sys/types.h>

src/sshagent/includes.h

@@ -0,0 +1,20 @@
+// mimic openSSH-portable's includes.h file to be able to use
+// its unmodified blowfish code
+
+#define HAVE_BLF_H
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE /* activate extra prototypes for glibc */
+#endif
+#include <sys/types.h>
+
+
+#ifdef _WIN32
+#include <stdint.h>
+
+typedef uint32_t u_int32_t;
+typedef uint16_t u_int16_t;
+typedef uint8_t u_int8_t;
+
+#define bzero(p,s) memset(p, 0, s)
+#endif