Reverse commit 4011ed4e31.

This commit was too broad and not cognizant of the purpose of the class
UTF8.

Add MAYBE_VERIFY_UTF8() macro, which can trap non-UTF8 encoded strings in
debug builds.

Use that macro conditionally in class UTF8 to trap non-UTF8 encoded strings
being put into UTF8 instances.

common/fp_lib_table.cpp

@@ -26,7 +26,6 @@
 
 #include <fctsys.h>
 #include <common.h>
-#include <macros.h>
 #include <kiface_i.h>
 #include <footprint_info.h>
 #include <lib_id.h>
@@ -287,12 +286,12 @@ MODULE* FP_LIB_TABLE::FootprintLoad( const wxString& aNickname, const wxString&
         LIB_ID& fpid = (LIB_ID&) ret->GetFPID();
 
         // Catch any misbehaving plugin, which should be setting internal footprint name properly:
-        wxASSERT( aFootprintName == FROM_UTF8( fpid.GetLibItemName() ) );
+        wxASSERT( aFootprintName == (wxString) fpid.GetLibItemName() );
 
         // and clearing nickname
         wxASSERT( !fpid.GetLibNickname().size() );
 
-        fpid.SetLibNickname( TO_UTF8( row->GetNickName() ) );
+        fpid.SetLibNickname( row->GetNickName() );
     }
 
     return ret;
@@ -310,7 +309,7 @@ FP_LIB_TABLE::SAVE_T FP_LIB_TABLE::FootprintSave( const wxString& aNickname,
         // Try loading the footprint to see if it already exists, caller wants overwrite
         // protection, which is atypical, not the default.
 
-        wxString fpname = FROM_UTF8( aFootprint->GetFPID().GetLibItemName() );
+        wxString fpname = aFootprint->GetFPID().GetLibItemName();
 
         std::unique_ptr<MODULE> footprint( row->plugin->FootprintLoad( row->GetFullURI( true ),
                                            fpname, row->GetProperties() ) );
@@ -360,8 +359,8 @@ void FP_LIB_TABLE::FootprintLibCreate( const wxString& aNickname )
 
 MODULE* FP_LIB_TABLE::FootprintLoadWithOptionalNickname( const LIB_ID& aFootprintId )
 {
-    wxString   nickname = FROM_UTF8( aFootprintId.GetLibNickname() );
-    wxString   fpname   = FROM_UTF8( aFootprintId.GetLibItemName() );
+    wxString   nickname = aFootprintId.GetLibNickname();
+    wxString   fpname   = aFootprintId.GetLibItemName();
 
     if( nickname.size() )
     {