Add small constants set, exit() and tests entry/exit

src/tests.asm

@@ -1 +1,18 @@
 %include "src/constants.asm"
+
+; core.asm
+extern	exit
+; console.asm
+; string.asm
+; convert.asm
+
+section .text
+	global _start
+_start:
+	push	rbp
+	mov	rbp, rsp
+	sub	rsp, SIZE_QWORD
+
+	leave
+	mov	rdi, 0
+	call	exit