c++tools: Fix (an) install issue

[Nathan Sidwell]

David reported an AIX problem, which I think this addresses.  I've not 
looked at pr98314 yet but there's certainly overlap

This fixes installers that don't understand -p.

	c++tools/
         (install): Do not use -p, use mkinstalldirs.
         (clean): Fix typo.

pushing to trunk
-- 
Nathan Sidwell
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