[gtkmm] TextIter: PredicateAdapter: Make constructor explicit.

[Murray Cumming <murrayc src gnome org>]

commit 5981fa1d4795f3d0636561fab2a90b2b01b26c02
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Dec 12 10:22:03 2016 +0100

    TextIter: PredicateAdapter: Make constructor explicit.
    
    Noticed by cppcheck.

 gtk/src/textiter.hg |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/src/textiter.hg b/gtk/src/textiter.hg
index 5e99d31..24c515e 100644
--- a/gtk/src/textiter.hg
+++ b/gtk/src/textiter.hg
@@ -91,7 +91,7 @@ protected:
   struct PredicateAdapter
   {
     Predicate predicate_;
-    inline PredicateAdapter(const Predicate& predicate);
+    inline explicit PredicateAdapter(const Predicate& predicate);
     static gboolean gtk_callback(gunichar uc, void* user_data);
   };