[PATCH] configure.ac: Include math.h when checking for sqrt/cbrt

[Mark Kettenis]

> From: Daniel Stone <daniel at fooishbar.org>
> Date: Mon, 26 Jul 2010 16:31:15 +0100
> 
> sqrt and cbrt are only defined in math.h, so we have to include that
> when checking for them, lest we miss it, and then some other header
> pulling in math.h causes build failures due to multiple definitions.

Eh, why?  AC_CHECK_LIB is supposed to check whether these symbols are
available in the given library in a way that doesn't depend on a
prototype for them being in scope.  So I don't see what you diff
achieves, other than adding more clutter to the configure scripts.