Custom mappings not being used

[cseickel]

User supplied mappings are not overriding the default ones.

EDIT: To be more precise, mappings with special characters, that may have multiple forms or are case insensitive, could create conflicts with default mappings. For example, a mapping of <BS> would not overwite the default mapping of <bs>, so both would be applied in an unknown order with unpredictable results.

The fix is to normalize those types of mapping to make sure that user supplied versions properly overwrite the default ones.