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/I18N.cpp

@@ -0,0 +1,11 @@
+#include "I18N.hpp"
+
+namespace Slic3r { namespace GUI { 
+
+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));
+}
+
+} }