(unwi_full_sigmask): Mark as HIDDEN.

(Logical change 1.149)
diff --git a/src/mi-init.c b/src/mi-init.c
index bb8ca71..666c06f 100644
--- a/src/mi-init.c
+++ b/src/mi-init.c
@@ -28,7 +28,7 @@
 #include "internal.h"
 #include "tdep.h"
 
-sigset_t unwi_full_sigmask;
+HIDDEN sigset_t unwi_full_sigmask;
 
 static const char rcsid[] UNUSED =
   "$Id: " PACKAGE_STRING " --- report bugs to " PACKAGE_BUGREPORT " $";