Make macro checks ARMv8-M baseline proof

libgloss:

        * arm/Makefile.in: Add newlib/libc/machine/arm to the include path if
        newlib is present.
        * arm/arm.h: Include acle-compat.h.
        (THUMB_V7_V6M): Rename to ...
        (PREFER_THUMB): This.  Use ACLE macros __ARM_ARCH_ISA_ARM instead of
        __ARM_ARCH_6M__ to decide whether to define it.
        (THUMB1_ONLY): Define for Thumb-1 only targets.
        (THUMB_V7M_V6M): Rename to ...
        (THUMB_VXM): This.  Defined based on __ARM_ARCH_ISA_ARM, excluding
        ARMv7.
        * arm/crt0.S: Use THUMB1_ONLY rather than __ARM_ARCH_6M__,
        !__ARM_ARCH_ISA_ARM rather than THUMB_V7M_V6M for fp enabling, and
        PREFER_THUMB rather than THUMB_V7_V6M.  Rename other occurences of
        THUMB_V7M_V6M to THUMB_VXM.
        * arm/linux-crt0.c: Likewise.
        * arm/redboot-crt0.S: Likewise.
        * arm/swi.h: Likewise.
        * arm/trap.S: Likewise.

newlib:

        * libc/machine/arm/memcpy-stub.c: Use ACLE macros __ARM_ARCH_ISA_THUMB
        and __ARM_ARCH_ISA_ARM to check for Thumb-2 only targets rather than
        __ARM_ARCH and __ARM_ARCH_PROFILE.
        * libc/machine/arm/memcpy.S: Likewise.
        * libc/machine/arm/setjmp.S: Likewise for Thumb-1 only target and
        include acle-compat.h.
        * libc/machine/arm/strcmp.S: Likewise for Thumb-1 and Thumb-2 only
        target and include acle-compat.h.
        * libc/sys/arm/arm.h: Include acle-compat.h.
        (THUMB_V7_V6M): Rename to ...
        (PREFER_THUMB): This.  Use ACLE macro __ARM_ARCH_ISA_ARM instead of
        __ARM_ARCH_6M__ to decide whether to define it.
        (THUMB1_ONLY): Define for Thumb-1 only targets.
        (THUMB_V7M_V6M): Rename to ...
        (THUMB_VXM): This.  Defined based on __ARM_ARCH_ISA_ARM, excluding
        ARMv7.
        * libc/sys/arm/crt0.S: Use PREFER_THUMB rather than THUMB_V7_V6M and
        rename THUMB_V7M_V6M into THUMB_VXM.
        * libc/sys/arm/swi.h: Likewise.

libgloss/arm/crt0.S

@@ -44,7 +44,7 @@
 /* .text is used instead of .section .text so it works with arm-aout too.  */
 	.text
 	.syntax unified
-#ifdef THUMB_V7_V6M
+#ifdef PREFER_THUMB
 	.thumb
 .macro FUNC_START name
 	.global \name
@@ -98,7 +98,7 @@
 
 	/*  stack limit is at end of data */
 	/*  allow slop for stack overflow handling and small frames */
-#ifdef __ARM_ARCH_6M__
+#ifdef THUMB1_ONLY
 	ldr	r0, .LC2
 	adds	r0, #128
 	adds	r0, #128
@@ -112,7 +112,7 @@
 	/*  Issue Angel SWI to read stack info */
 	movs	r0, #AngelSWI_Reason_HeapInfo
 	adr	r1, .LC0	/*  point at ptr to 4 words to receive data */
-#ifdef THUMB_V7M_V6M
+#ifdef THUMB_VXM
 	bkpt	AngelSWI
 #elif defined(__thumb2__)
 	/*  We are in thumb mode for startup on armv7 architectures. */
@@ -154,7 +154,7 @@
 	cmp	r2, #0
 	beq	.LC27
 	/*  allow slop for stack overflow handling and small frames */
-#ifdef __ARM_ARCH_6M__
+#ifdef THUMB1_ONLY
 	adds	r2, #128
 	adds	r2, #128
 	mov	sl, r2
@@ -180,7 +180,7 @@
 #ifdef __thumb2__
 	it	eq
 #endif	
-#ifdef __ARM_ARCH_6M__
+#ifdef THUMB1_ONLY
 	bne	.LC28
 	ldr	r3, .LC0
 .LC28:
@@ -192,7 +192,7 @@
 		 have somehow missed it below (in which case it gets the same
 		 value as FIQ - not ideal, but better than nothing.) */
 	mov	sp, r3
-#ifdef THUMB_V7_V6M
+#ifdef PREFER_THUMB
 	/* XXX Fill in stack assignments for interrupt modes.  */
 #else
 	mrs	r2, CPSR
@@ -235,7 +235,7 @@
 	   this default 64k is enough for the program being executed.
 	   However, it ensures that this simple crt0 world will not
 	   immediately cause an overflow event:  */
-#ifdef __ARM_ARCH_6M__
+#ifdef THUMB1_ONLY
 	movs	r2, #64
 	lsls	r2, r2, #10
 	subs	r2, r3, r2
@@ -255,7 +255,7 @@
 	subs	a3, a3, a1		/* Third arg: length of block */
 	
 
-#if defined(__thumb__) && !defined(THUMB_V7_V6M)
+#if __thumb__ && !defined(PREFER_THUMB)
 	/* Enter Thumb mode.... */
 	add	a4, pc, #1	/* Get the address of the Thumb block */
 	bx	a4		/* Go there and start Thumb decoding  */
@@ -426,7 +426,7 @@ __change_mode:
 
 	bl	FUNCTION (exit)		/* Should not return.  */
 
-#if defined(__thumb__) && !defined(THUMB_V7_V6M)
+#if __thumb__ && !defined(PREFER_THUMB)
 	/* Come out of Thumb mode.  This code should be redundant.  */
 
 	mov	a4, pc