[glibmm] gmmproc: swap() implementations: Use std::swap().

[Murray Cumming <murrayc src gnome org>]

commit ddec69b2fafc7c448f330dfd23e77d94c33d2d82
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Jul 28 10:58:42 2016 +0200

    gmmproc: swap() implementations: Use std::swap().
    
    Because this simplifies the code.

 tools/m4/class_boxedtype.m4       |    4 +---
 tools/m4/class_opaque_copyable.m4 |    4 +---
 2 files changed, 2 insertions(+), 6 deletions(-)
---
diff --git a/tools/m4/class_boxedtype.m4 b/tools/m4/class_boxedtype.m4
index ae0a92e..a5046f5 100644
--- a/tools/m4/class_boxedtype.m4
+++ b/tools/m4/class_boxedtype.m4
@@ -175,9 +175,7 @@ dnl This could be a free or an unref, we do not need to know.
 
 void __CPPNAME__::swap(__CPPNAME__& other) noexcept
 {
-  __CNAME__ *const temp = gobject_;
-  gobject_ = other.gobject_;
-  other.gobject_ = temp;
+  std::swap(gobject_, other.gobject_);
 }
 
 __CNAME__* __CPPNAME__::gobj_copy() const
diff --git a/tools/m4/class_opaque_copyable.m4 b/tools/m4/class_opaque_copyable.m4
index 26148e9..7e04921 100644
--- a/tools/m4/class_opaque_copyable.m4
+++ b/tools/m4/class_opaque_copyable.m4
@@ -166,9 +166,7 @@ __CPPNAME__::~__CPPNAME__`'() noexcept
 
 void __CPPNAME__::swap(__CPPNAME__& other) noexcept
 {
-  __CNAME__ *const temp = gobject_;
-  gobject_ = other.gobject_;
-  other.gobject_ = temp;
+  std::swap(gobject_, other.gobject_);
 }
 
 __CNAME__* __CPPNAME__::gobj_copy() const