patch 8.0.1506: new version of HP NonStop (Tandem) doesn't like a header

Problem:    New version of HP NonStop (Tandem) doesn't like the default header
            for setenv().
Solution:   Put a #ifdef around the setenv() entry. (Joachim Schmitz)
diff --git a/src/osdef2.h.in b/src/osdef2.h.in
index 330a5a4..f29451d 100644
--- a/src/osdef2.h.in
+++ b/src/osdef2.h.in
@@ -8,7 +8,11 @@
 extern char	*malloc(unsigned int);
 extern char	*realloc(char *, int);
 extern char	*getenv(char *);
+#ifndef __TANDEM
 extern int	setenv(char *, char *, int);
+#else
+extern int	setenv(const char *, const char *, int);
+#endif
 extern int	putenv(const char *);
 
 #ifndef __TANDEM