[NaCl SDK] nacl_io: Add support for non-blocking connect/accept

Move the socket calls that depend on the handle state
into kernel_handle.h/cc.

TEST=new unittest + libcurl and thttpd from naclports
BUG=
R=noelallen@chromium.org

Review URL: https://codereview.chromium.org/26703008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228290 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228290