Bug 958234: Rename xptc{invoke,stubs}_asm_ppc_openbsd.s to .S to fix build on OpenBSD/powerpc after bug 932178 r=froydnj

--HG--
rename : xpcom/reflect/xptcall/src/md/unix/xptcinvoke_asm_ppc_openbsd.s => xpcom/reflect/xptcall/src/md/unix/xptcinvoke_asm_ppc_openbsd.S
rename : xpcom/reflect/xptcall/src/md/unix/xptcstubs_asm_ppc_openbsd.s => xpcom/reflect/xptcall/src/md/unix/xptcstubs_asm_ppc_openbsd.S