Suggestions (#1)

* Update main.s

- replaced .asciz with .ascii to avoid an additional zero byte allocation
- removed unnecessary section headers not needed by linker
- added extern section for importing sol_log_

* Update main.s

removed leading .

* Update main.s

Seems we don't need the extern declaration after all!

helloworld/asm/main.s

@@ -1,10 +1,8 @@
-	.text
-	.globl	entrypoint
+.globl entrypoint
 entrypoint:
 	lddw r1, .message
 	mov64 r2, 12
 	call sol_log_
 	exit
-	.section	.rodata
-.message:
-	.asciz	"Hello world!"
+.rodata 
+	message: .ascii "Hello world!"