Fix incorrect line counting when running REPT blocks.

Fixes #461

test/asm/rept-line-no.asm

@@ -0,0 +1,8 @@
+
+	WARN "Line 2"
+REPT 3
+
+	WARN "Line 5"
+
+ENDR
+	WARN "Line 8"

test/asm/rept-line-no.out

@@ -0,0 +1,10 @@
+warning: rept-line-no.asm(2): [-Wuser]
+    Line 2
+warning: rept-line-no.asm(3) -> rept-line-no.asm::REPT~1(5): [-Wuser]
+    Line 5
+warning: rept-line-no.asm(3) -> rept-line-no.asm::REPT~2(5): [-Wuser]
+    Line 5
+warning: rept-line-no.asm(3) -> rept-line-no.asm::REPT~3(5): [-Wuser]
+    Line 5
+warning: rept-line-no.asm(8): [-Wuser]
+    Line 8