[glibmm] convert_glib.m4: Remove some unusued conversions

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 8c4aad91e743414503e7abae0d67bb7fe1be3b41
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Mar 1 15:24:23 2018 +0100

    convert_glib.m4: Remove some unusued conversions
    
    These conversions are not used in glibmm. If they are used anywhere else,
    they should be defined where they are used.

 tools/m4/convert_glib.m4 |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)
---
diff --git a/tools/m4/convert_glib.m4 b/tools/m4/convert_glib.m4
index 8d32659..87197e4 100644
--- a/tools/m4/convert_glib.m4
+++ b/tools/m4/convert_glib.m4
@@ -88,7 +88,6 @@ define(`__GCHARP_TO_STDSTRING',`Glib::convert_const_gchar_ptr_to_stdstring($`'3)
 _CONVERSION(`const Glib::ustring&',`const char*',`$3.c_str()')
 _CONVERSION(`const Glib::ustring&', `const guchar*', `(($2)$3.c_str())')
 _CONVERSION(`const std::string&',`const char*',`$3.c_str()')
-_CONVERSION(`std::string',`const char*',`$3.c_str()')
 _CONVERSION(`const Glib::ustring&',`gchar*',`const_cast<gchar*>($3.c_str())')
 _CONVERSION(`const-gchar*',`Glib::ustring',__GCHARP_TO_USTRING)
 _CONVERSION(`const-guchar*',`Glib::ustring',__GCHARP_TO_USTRING)
@@ -99,9 +98,6 @@ _CONVERSION(`const char*',`std::string',__GCHARP_TO_STDSTRING)
 _CONVERSION(`const char*',`const-gchar*',`$3')
 _CONVERSION(`const-gchar*',`const char*',`$3')
 _CONVERSION(`const char*',`const std::string&',__GCHARP_TO_STDSTRING)
-_CONVERSION(`std::string', `char*', `g_strdup(($3).c_str())')
-_CONVERSION(`const std::string&', `char*', `g_strdup(($3).c_str())')
-_CONVERSION(`Glib::ustring', `char*', `g_strdup(($3).c_str())')
 
 _CONVERSION(`return-gchar*',`Glib::ustring',`Glib::convert_return_gchar_ptr_to_ustring($3)')
 _CONVERSION(`return-gchar*',`std::string',`Glib::convert_return_gchar_ptr_to_stdstring($3)')