Add %elif preprocessor test

test/elif.asm

@@ -0,0 +1,36 @@
+%macro DosPrintMsg 1+
+%ifnid %1
+section .data
+%%str_to_print:db %1
+section .text
+ mov dx,%%str_to_print
+ mov ah,9
+ int 0x21
+%else
+ mov dx,(%1)
+ mov ah,9
+ int 0x21
+%endif
+%endmacro
+
+%macro DosExit 1
+%if (%1) == 0
+;use short-form return 0 exit
+ int 0x20
+%elif ((%1) < 256) && ((%1) > 0)
+ mov ax,0x4C00 | (%1)
+ int 0x21
+%else
+%error Invalid return value
+%endif
+%endmacro
+
+org 0x100
+ DosPrintMsg predefined_str
+ DosPrintMsg "Using string with macro-defined label",10,0
+ DosExit 0
+ DosExit 1
+ DosExit 256
+
+section .data
+predefined_str:db "Using string with predefined label",10,0