Sync qemuppc with linuxppc.

- Don't reverse bitfields; do use ego (41f3bf7).
 - Use MACHOPT_F=-m2 (3dae9e4).
 - Remove old trap.s (26de4c1).

At this commit, one can build qemuppc with mcg by editing the root
build.lua to uncomment "qemuppc" in "vars.plats".  If one also
uncomments "qemuppc" from "vars.plats_with_tests", then mcg fails to
build the tests.  If one uses ncg (by editing plat/qemuppc/descr to
change "mcg" to "ncg"), then the tests pass.

plat/qemuppc/descr

@@ -19,11 +19,8 @@ var PLATFORM=qemuppc
 var PLATFORMDIR={EM}/share/ack/{PLATFORM}
 var CPP_F=-D__unix
 var ALIGN=-a0:4 -a1:4 -a2:4 -a3:4 -b0:0x01000000
-var C_LIB={PLATFORMDIR}/libc-ansi.a
-# bitfields reversed for compatibility with (g)cc.
-var CC_ALIGN=-Vr
-var OLD_C_LIB={C_LIB}
-var MACHOPT_F=
+var MACHOPT_F=-m2
+var EGO_PLAT_FLAGS=-M{EM}/share/ack/ego/{ARCH}.descr
 
 # Override the setting in fe so that files compiled for qemuppc can see
 # the platform-specific headers.

plat/qemuppc/libsys/trap.s

@@ -1,65 +0,0 @@
-#
-! $Source: /cvsroot/tack/Ack/plat/linux386/libsys/_syscall.s,v $
-! $State: Exp $
-! $Revision: 1.1 $
-
-! Declare segments (the order is important).
-
-.sect .text
-.sect .rom
-.sect .data
-.sect .bss
-
-.sect .text
-
-#define IFFALSE 4
-#define IFTRUE 12
-#define ALWAYS 20
-
-#define LT 0
-#define GT 1
-#define EQ 2
-#define OV 3
-
-EARRAY	=  0
-ERANGE	=  1
-ESET	=  2
-EIOVFL	=  3
-EFOVFL	=  4
-EFUNFL	=  5
-EIDIVZ	=  6
-EFDIVZ	=  7
-EIUND	=  8
-EFUND	=  9
-ECONV	= 10
-ESTACK  = 16
-EHEAP	= 17
-EILLINS = 18
-EODDZ	= 19
-ECASE	= 20
-EMEMFLT	= 21
-EBADPTR = 22
-EBADPC  = 23
-EBADLAE = 24
-EBADMON = 25
-EBADLIN = 26
-EBADGTO = 27
-EUNIMPL = 63		! unimplemented em-instruction called
-
-.define .trap_ecase
-.trap_ecase:
-	b .trp
-
-.define .trap_earray
-.trap_earray:
-	b .trp
-
-.define .trap_erange
-.trap_erange:
-	b .trap
-
-.define .trp
-.define .trap
-.trp:
-.trap:
-	b .trp					! spin forever