config.gcc: Expunge references to alpha/t-pe...

	* config.gcc: Expunge references to alpha/t-pe, pa/t-openbsd,
	x-linux-aout, i386/t-go32, t-osf, m68k/x-m68kv,
	ns32k/xm-netbsd.h, rs6000/t-openbsd, rs6000/t-xnewas,
	rs6000/x-aix41-gld.  These are nonexistent, empty, or obsolete.

	(i750a-*-*): Error here if hosting on i750a.
	(alpha*-*-winnt*, ix86-*-winnt3*): Remove stanzas entirely.

	* x-linux-aout, xm-freebsd.h, i386/beos-pe.h, ns32k/xm-netbsd.h:
	Remove (empty modulo comments).

	* 1750a/xm-1750a.h, alpha/config-nt.sed, alpha/win-nt.h,
	alpha/xm-winnt.h, i386/config-nt.sed, i386/os2.h,
	i386/t-winnt, i386/win-nt.h, i386/xm-freebsd.h, i386/xm-os2.h,
	i386/xm-winnt.h, m68k/x-alloca-c, m88k/x-dguxbcs,
	mips/x-netbsd, mips/x-nws3250v4, rs6000/t-xnewas,
	rs6000/t-xrs6000, rs6000/xm-cygwin.h: Remove (obsolete)

	* i386/crtdll.h, i386/cygwin.h, i386/mingw32.h:
	Remove reference to winnt.h in comment.
	* rs6000/t-newas, rs6000/t-rs6000: Override LIBGCC1_TEST to null.

From-SVN: r40044