Let template set tell us what the valid non-breaking space is for the target output...

Let template set tell us what the valid non-breaking space is for the target output format.  This is somewhat inefficient (although so far only found one place to use it - commit coming later); faster design choice might be to create a <template_name>_functions.php file in the template set's directory, where a function called <template_name>_non_breaking_space() can be called, but then where do you draw the line? (Could also replace the hyperlink.tpl file, but then it starts to look like you are doing exactly what the template engine is supposed to be doing.)

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