Move DEF_WEAK into defines.h.

As well pull in more recent changes from OpenBSD these will start to
arrive so put it where the definition is shared.

defines.h

@@ -832,6 +832,13 @@ struct winsize {
 # define SSH_IOBUFSZ 8192
 #endif
 
+/*
+ * We want functions in openbsd-compat, if enabled, to override system ones.
+ * We no-op out the weak symbol definition rather than remove it to reduce
+ * future sync problems.
+ */
+#define DEF_WEAK(x)
+
 /*
  * Platforms that have arc4random_uniform() and not arc4random_stir()
  * shouldn't need the latter.

openbsd-compat/vis.c

@@ -33,12 +33,6 @@
 #include "includes.h"
 #if !defined(HAVE_STRNVIS) || defined(BROKEN_STRNVIS)
 
-/*
- * We want these to override in the BROKEN_STRNVIS case.  TO avoid future sync
- * problems no-op out the weak symbol definition rather than remove it.
- */
-#define DEF_WEAK(x)
-
 #include <sys/types.h>
 #include <errno.h>
 #include <ctype.h>