[objc, testsuite] Correct some objc.dg-struct-layout-encoding-1/t0[23]?_main.m XFAILs (PR objc/45989)

[Mike Stump]

On Jan 14, 2011, at 9:13 AM, Rainer Orth wrote:
> Currently, some objc.dg-struct-layout-encoding-1/t0*_main.m execution
> tests XPASS on many platforms.  The following patch, developed primarily
> by Dominique with a few suggestions from myself, corrects this.
> 
> Tested on i386-pc-solaris2.11 and sparc-sun-solaris2.11, ok for
> mainline?

Ok.