lib symbols: make fp filter tolerant to spaces in names.

For historical reasons they are stored in a string using spaces as separators.
So each fp filter is now escaped to remove spaces (replaced by {space})
Fixes #9009
https://gitlab.com/kicad/code/kicad/issues/9009

common/string_utils.cpp

@@ -211,6 +211,15 @@ wxString EscapeString( const wxString& aSource, ESCAPE_CONTEXT aContext )
             else
                 converted += c;
         }
+        else if( aContext == CTX_NO_SPACE )
+        {
+            if( c == ' ' )
+                converted += "{space}";
+            else if( c == '{' )
+                converted += "{brace}";
+            else
+                converted += c;
+        }
         else
             converted += c;
     }