Regression from issue #348 with nbsp and other entities

[michaelrsweet]

The fixes for issue #348 have caused a regression with   and probably all entities that don't map to a US ASCII character.

[michaelrsweet]

@RekGRpth proposed a fix that is close to the right one - the iso8859() function isn't aware of the UTF-8 handling that was added, and so it doesn't do the necessary lookups.

[michaelrsweet]

[master 712f7ee] Fix HTML entitites in UTF-8 mode (Issue #401).