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/Plater.hpp

@@ -14,6 +14,7 @@ class wxButton;
 class wxBoxSizer;
 class wxGLCanvas;
 class wxScrolledWindow;
+class wxString;
 
 namespace Slic3r {