Make using local IDs in @if directives an error.

Addresses BIT-1296.

testing/btest/language/at-if-invalid.bro

@@ -0,0 +1,41 @@
+# @TEST-EXEC-FAIL: bro -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+function foo(c: count): bool
+	{ return c == 42 ? T : F; }
+
+global TRUE_CONDITION = T;
+
+event bro_init()
+	{
+	local xyz = 0;
+	local local_true_condition = T;
+
+	@if ( F )
+		xyz += 1;
+	@endif
+
+	@if ( foo(0) )
+		xyz += 1;
+	@endif
+
+	@if ( T && foo(42) )
+		xyz += 2;
+	@endif
+
+	xyz = 0;
+
+	@if ( F && foo(xyz) )
+		xyz += 1;
+	@else
+		xyz += 2;
+	@endif
+
+	xyz = 0;
+
+	@if ( T && TRUE_CONDITION && local_true_condition )
+		xyz += 1;
+	@else
+		xyz += 2;
+	@endif
+	}