Removed some obsolete Perl bindings.

Removed libslic3r from the default include paths for all modules but
libslic3r. Now headers from libslic3r need to be included with an
explicit path (libslic3r/libslic3r.h etc)
Split the localization macros into I18N.{cpp,h}

src/slic3r/GUI/GUI.cpp

@@ -1,5 +1,6 @@
 #include "GUI.hpp"
 #include "GUI_App.hpp"
+#include "I18N.hpp"
 #include "WipeTowerDialog.hpp"
 
 #include <assert.h>
@@ -33,8 +34,8 @@
 #include "PresetBundle.hpp"
 #include "UpdateDialogs.hpp"
 
-#include "../../libslic3r/Utils.hpp"
-#include "../../libslic3r/Print.hpp"
+#include "libslic3r/Utils.hpp"
+#include "libslic3r/Print.hpp"
 
 namespace Slic3r { namespace GUI {
 
@@ -307,12 +308,6 @@ AppConfig* get_app_config()
     return wxGetApp().app_config;
 }
 
-wxString L_str(const std::string &str)
-{
-	//! Explicitly specify that the source string is already in UTF-8 encoding
-	return wxGetTranslation(wxString(str.c_str(), wxConvUTF8));
-}
-
 wxString from_u8(const std::string &str)
 {
 	return wxString::FromUTF8(str.c_str());