Add test case for istruc's "at" with local labels

Signed-off-by: Sławomir Bocheński <lkslawek@gmail.com>

test/istruc_local.asm

@@ -0,0 +1,37 @@
+;Testname=test; Arguments=-fbin -oistruc_local.bin; Files=stdout stderr istruc_local.bin
+
+struc Struc1
+    .dword: resd 1
+    .word: resw 1
+endstruc
+
+struc Struc2
+    .word: resw 1
+    .dword: resd 1
+endstruc
+
+; The following returned error about negative values for TIMES in nasm 2.15.05
+; because local labels seemingly matching Struc1 have been replaced by those in
+; Struc2.
+
+istruc Struc1
+    at .dword, dd 0xffffffff
+    at .word, dw 0x1111
+iend
+
+; The following two just didn't work as istruc was just literally outputting
+; local labels which are unknown after a global label appears.
+
+struc1:
+
+istruc Struc1
+    at .dword, dd 0x78563412
+    at .word, dw 0xbc9a
+iend
+
+struc2:
+
+istruc Struc2
+    at .word, dw 0xbc9a
+    at .dword, dd 0x78563412
+iend