Fix return of cexp for NaN + 0i.

Fixes the return value of cexp to match Annex G.6.3.1; when the
parameter is NaN + 0i, we should return NaN + 0i, and not
NaN + NaN.

mingw-w64-crt/ChangeLog:

2010-06-27  Doug Semler  <dougsemler@gmail.com>

	* new_complex/cexp.def.h (cexp): Return imaginary zero when NaN + 0i.

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@2672 4407c894-4637-0410-b4f5-ada5f102cad1