Make considerably more progress on AARCH64

- Utilities like pledge.com now build
- kprintf() will no longer balk at 48-bit addresses
- There's a new aarch64-dbg build mode that should work
- gc() and defer() are mostly pacified; avoid using them on aarch64
- THIRD_PART_STB now has Arm Neon intrinsics for fast image handling

libc/sysv/syscount.S

@@ -24,6 +24,7 @@
 //	for the purpose of counting non-Windows system calls. Please
 //	note wrappers may still short circuit calls sometimes, which
 //	wouldn't impact this counter.
+
 	.bss
 	.balign	8
 __syscount:
@@ -31,6 +32,8 @@ __syscount:
 	.endobj	__syscount,globl
 	.previous
 
+#ifdef __x86_64__
+
 	.initbss 701,_init___syscount
 __syscount_next:
 	.quad	0
@@ -49,3 +52,5 @@ syscount:
 	ezlea	syscount,ax
 	mov	%rax,__systemfive(%rip)
 	.init.end 701,_init___syscount
+
+#endif /* __x86_64__ */