Ensure paths and filenames are always stored with '/' as separator in fp_lib_table, like in other kicad files.

Ensure also paths and filenames read from a fp_lib_table always use '/' as separator (works fine on Windows)
Fixes: lp:1658534
https://bugs.launchpad.net/kicad/+bug/1658534

common/lib_table_base.cpp

@@ -83,10 +83,15 @@ const wxString LIB_TABLE_ROW::GetFullURI( bool aSubstituted ) const
 void LIB_TABLE_ROW::Format( OUTPUTFORMATTER* out, int nestLevel ) const
     throw( IO_ERROR, boost::interprocess::lock_exception )
 {
+    // In Kicad, we save path and file names using the Unix notation (separator = '/')
+    // So ensure separator is always '/' is saved URI string
+    wxString uri = GetFullURI();
+    uri.Replace( '\\', '/' );
+
     out->Print( nestLevel, "(lib (name %s)(type %s)(uri %s)(options %s)(descr %s))\n",
                 out->Quotew( GetNickName() ).c_str(),
                 out->Quotew( GetType() ).c_str(),
-                out->Quotew( GetFullURI() ).c_str(),
+                out->Quotew( uri ).c_str(),
                 out->Quotew( GetOptions() ).c_str(),
                 out->Quotew( GetDescr() ).c_str()
                 );
@@ -143,7 +148,17 @@ void LIB_TABLE_ROW::Parse( std::unique_ptr< LIB_TABLE_ROW >& aRow, LIB_TABLE_LEX
                 in->Duplicate( tok );
             sawUri = true;
             in->NeedSYMBOLorNUMBER();
-            aRow->SetFullURI( in->FromUTF8() );
+            // Saved path and file names use the Unix notation (separator = '/')
+            // However old files, and files edited by hands can use the woindows
+            // separator. Force the unix notation
+            // (It works on windows, and moreover, wxFileName and wxDir takes care to that
+            // on windows)
+            // moreover, URLs use the '/' as separator
+            {
+            wxString uri = in->FromUTF8();
+            uri.Replace( '\\', '/' );
+            aRow->SetFullURI( uri );
+            }
             break;
 
         case T_type: