Get rid of unsed since rev 1.109 of lib/Makefile WANT_CSRG_LIBM define.
Get rid of unsed since rev 1.109 of lib/Makefile WANT_CSRG_LIBM define.

We'll never install math.h wrapped by this define since msun's math.h
is using, so it should be removed from the source tree at some point
(after merge of useful stuff to msun's math.h which is installing now
to /usr/include)

Reviewed by:    bde

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