Fix compilation of nbd on Solaris (Andreas Faerber)

Fix compilation of nbd on Solaris (Andreas Faerber)

Compilation of QEMU is currently broken on Solaris due to nbd's use of _IO and
due to network libraries not being linked into qemu-img.

The attached patch adds the appropriate libraries (copied from Makefile.target)
and includes an additional Sun-specific header for _IO.

With these fixes it compiles okay, on OpenSolaris snv_93 (amd64).

Signed-off-by: Andreas Faerber <andreas.faerber@web.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4982 c046a42c-6fe2-441c-8c8c-71466251a162